# Setting up TCP/IP on NetBSD in practice
## A walk through the kernel configuration
Before we dive into configuring various aspects of network setup, we want to
walk through the necessary bits that have to or can be present in the kernel.
See [[Compiling the kernel|guide/kernel]] for more details on compiling the
kernel, we will concentrate on the configuration of the kernel here. We will
take the i386/GENERIC config file as an example here. Config files for other
platforms should contain similar information, the comments in the config files
give additional hints. Besides the information given here, each kernel option is
also documented in the
manpage, and there is usually a manpage for each driver too, e.g.
The first line of each config file shows the version. It can be used to compare
against other versions via CVS, or when reporting bugs.
options NTP # NTP phase/frequency locked loop
If you want to run the Network Time Protocol (NTP), this option can be enabled
for maximum precision. If the option is not present, NTP will still work. See
file-system NFS # Network File System client
If you want to use another machine's hard disk via the Network File System
(NFS), this option is needed. The guide article about the
[[Network File System|guide/net-services#nfs]] gives more information on NFS.
options NFSSERVER # Network File System server
This option includes the server side of the NFS remote file sharing protocol.
Enable if you want to allow other machines to use your hard disk. The mentioned
article in the guide about [[NFS|guide/net-services#nfs]] contains more
information on NFS.
#options GATEWAY # packet forwarding
If you want to setup a router that forwards packets between networks or network
interfaces, setting this option is needed. It doesn't only switch on packet
forwarding, but also increases some buffers. See
options INET # IP + ICMP + TCP + UDP
This enables the TCP/IP code in the kernel. Even if you don't want/use
networking, you will still need this for machine-internal communication of
subsystems like the X Window System. See
options INET6 # IPV6
If you want to use IPv6, this is your option. If you don't want IPv6, which is
part of NetBSD since the 1.5 release, you can remove/comment out that option.
manpage and [[Next generation Internet protocol -
IPv6|guide/net-intro#ipv6-intro]] for more information on the next generation
#options IPSEC # IP security
Includes support for the IPsec protocol, including key and policy management,
authentication and compression. This option can be used without the previous
option INET6, if you just want to use IPsec with IPv4, which is possible. See
#options IPSEC_ESP # IP security (encryption part; define w/IPSEC)
This option is needed in addition to IPSEC if encryption is wanted in IPsec.
#options MROUTING # IP multicast routing
If multicast services like the MBone services should be routed, this option
needs to be included. Note that the routing itself is controlled by the
options ISO,TPIP # OSI
#options EON # OSI tunneling over IP
These options include the OSI protocol stack, which was said for a long time to
be the future of networking. It's mostly history these days. :-) See the
for more information.
options NETATALK # AppleTalk networking protocols
Include support for the AppleTalk protocol stack. Userland server programs are
needed to make use of that. See pkgsrc/net/netatalk and pkgsrc/net/netatalk-asun
for such packages. More information on the AppleTalk protocol and protocol stack
are available in the
options PPP_BSDCOMP # BSD-Compress compression support for PPP
options PPP_DEFLATE # Deflate compression support for PPP
options PPP_FILTER # Active filter support for PPP (requires bpf)
These options tune various aspects of the Point-to-Point protocol. The first two
determine the compression algorithms used and available, while the third one
enables code to filter some packets.
options PFIL_HOOKS # pfil(9) packet filter hooks
options IPFILTER_LOG # ipmon(8) log support
These options enable firewalling in NetBSD, using IPFilter. See the
for more information on operation of IPFilter, and [[Configuring the
gateway/firewall|guide/net-practice#ipnat-configuring-gateway]] for a
# Compatibility with 4.2BSD implementation of TCP/IP. Not recommended.
This option is only needed if you have machines on the network that still run
4.2BSD or a network stack derived from it. If you've got one or more
4.2BSD-systems on your network, you've to pay attention to set the right
broadcast-address, as 4.2BSD has a bug in its networking code, concerning the
broadcast address. This bug forces you to set all host-bits in the
broadcast-address to `0`. The `TCP_COMPAT_42` option helps you ensuring this.
These options enable lookup of data via DHCP or the BOOTPARAM protocol if the
kernel is told to use a NFS root file system. See the
manpage for more information.
# Kernel root file system and dump configuration.
config netbsd root on ? type ?
#config netbsd root on sd0a type ffs
#config netbsd root on ? type nfs
These lines tell where the kernel looks for its root file system, and which
filesystem type it is expected to have. If you want to make a kernel that uses a
NFS root filesystem via the tlp0 interface, you can do this with
root on tlp0 type nfs
If a `?` is used instead of a device/type, the kernel tries to
figure one out on its own.
# ISA serial interfaces
com0 at isa? port 0x3f8 irq 4 # Standard PC serial ports
com1 at isa? port 0x2f8 irq 3
com2 at isa? port 0x3e8 irq 5
If you want to use PPP or SLIP, you will need some serial (com) interfaces.
Others with attachment on USB, PCMCIA or PUC will do as well.
# Network Interfaces
This rather long list contains all sorts of network drivers. Please pick the one
that matches your hardware, according to the comments. For most drivers, there's
also a manual page available, e.g.
# MII/PHY support
This section lists media independent interfaces for network cards. Pick one that
matches your hardware. If in doubt, enable them all and see what the kernel
picks. See the
for more information.
# USB Ethernet adapters
aue* at uhub? port ? # ADMtek AN986 Pegasus based adapters
cue* at uhub? port ? # CATC USB-EL1201A based adapters
kue* at uhub? port ? # Kawasaki LSI KL5KUSB101B based adapters
USB-ethernet adapters only have about 2MBit/s bandwidth, but they are very
convenient to use. Of course this needs other USB related options which we won't
cover here, as well as the necessary hardware. See the corresponding manpages
for more information.
# network pseudo-devices
pseudo-device bpfilter 8 # Berkeley packet filter
This pseudo-device allows sniffing packets of all sorts. It's needed for
tcpdump, but also rarpd and some other applications that need to know about
network traffic. See
[bpf(4)](http://netbsd.gw.com/cgi-bin/man-cgi?bpf+4+NetBSD-5.0.1+i386) for more
pseudo-device ipfilter # IP filter (firewall) and NAT
This one enables the IPFilter's packet filtering kernel interface used for
firewalling, NAT (IP Masquerading) etc. See
[Configuring the gateway/firewall|guide/net-practice#ipnat-configuring-gateway]]
for more information.
pseudo-device loop # network loopback
This is the `lo0` software loopback network device which is used by some
programs these days, as well as for routing things. It should not be omitted.
See [lo(4)](http://netbsd.gw.com/cgi-bin/man-cgi?lo+4+NetBSD-5.0.1+i386) for
pseudo-device ppp 2 # Point-to-Point Protocol
If you want to use PPP either over a serial interface or ethernet (PPPoE), you
will need this option. See
details on this interface.
pseudo-device sl 2 # Serial Line IP
Serial Line IP is a simple encapsulation for IP over (well :) serial lines. It
does not include negotiation of IP addresses and other options, which is the
reason that it's not in widespread use today any more. See
pseudo-device strip 2 # Starmode Radio IP (Metricom)
If you happen to have one of the old Metricom Ricochet packet radio wireless
network devices, use this pseudo-device to use it. See the
manpage for detailed information.
pseudo-device tun 2 # network tunneling over tty
This network device can be used to tunnel network packets to a device file,
`/dev/tun*`. Packets routed to the tun0 interface can be read from `/dev/tun0`,
and data written to `/dev/tun0` will be sent out the tun0 network interface.
This can be used to implement e.g. QoS routing in userland. See
pseudo-device gre 2 # generic L3 over IP tunnel
The GRE encapsulation can be used to tunnel arbitrary layer 3 packets over IP,
e.g. to implement VPNs. See
[gre(4)](http://netbsd.gw.com/cgi-bin/man-cgi?gre+4+NetBSD-5.0.1+i386) for more.
pseudo-device gif 4 # IPv over IPv tunnel (RFC 1933)
Using the GIF interface allows to tunnel e.g. IPv6 over IPv4, which can be used
to get IPv6 connectivity if no IPv6-capable uplink (ISP) is available. Other
mixes of operations are possible, too. See the
for some examples.
#pseudo-device faith 1 # IPv tcp relay translation i/f
The faith interface captures IPv6 TCP traffic, for implementing userland
IPv6-to-IPv4 TCP relays e.g. for protocol transitions. See the
manpage for more details on this device.
#pseudo-device stf 1 # 6to4 IPv6 over IPv4 encapsulation
This adds a network device that can be used to tunnel IPv6 over IPv4 without
setting up a configured tunnel before. The source address of outgoing packets
contains the IPv4 address, which allows routing replies back via IPv4. See the
and [IPv6 Connectivity & Transition via 6to4|guide/net-practice#ipv6-6to4]] for
pseudo-device vlan # IEEE 802.1q encapsulation
This interface provides support for IEEE 802.1Q Virtual LANs, which allows
tagging Ethernet frames with a `vlan` ID. Using properly configured switches
(that also have to support VLAN, of course), this can be used to build virtual
LANs where one set of machines doesn't see traffic from the other (broadcast and
tells more about this.
## Overview of the network configuration files
The following is a list of the files used to configure the network. The usage of
these files, some of which have already been met the first chapters, will be
described in the following sections.
* `/etc/hosts` -- Local hosts database file. Each line contains information
regarding a known host and contains the internet address, the host's name and
the aliases. Small networks can be configured using only the hosts file,
without a *name server*.
* `/etc/resolv.conf` -- This file specifies how the routines which provide
access to the Internet Domain Name System should operate. Generally it
contains the addresses of the name servers.
* `/etc/ifconfig.xxx` -- This file is used for the automatic configuration of
the network card at boot.
* `/etc/mygate` -- Contains the IP address of the gateway.
* `/etc/nsswitch.conf` -- Name service switch configuration file. It controls
how a process looks up various databases containing information regarding
hosts, users, groups, etc. Specifically, this file defines the order to look
up the databases. For example, the line:
hosts: files dns
specifies that the hosts database comes from two sources, *files* (the local
`/etc/hosts` file) and *DNS*, (the Internet Domain Name System) and that the
local files are searched before the DNS.
It is usually not necessary to modify this file.
## Connecting to the Internet with a modem
There are many types of Internet connections: this section explains how to
connect to a provider using a modem over a telephone line using the PPP
protocol, a very common setup. In order to have a working connection, the
following steps must be done:
1. Get the necessary information from the provider.
2. Edit the file `/etc/resolv.conf` and check `/etc/nsswitch.conf`.
3. Create the directories `/etc/ppp` and `/etc/ppp/peers` if they don't exist.
4. Create the connection script, the chat file and the pppd options file.
5. Created the user-password authentication file.
Judging from the previous list it looks like a complicated procedure that
requires a lot of work. Actually, the single steps are very easy: it's just a
matter of modifying, creating or simply checking some small text files. In the
following example it will be assumed that the modem is connected to the second
serial port `/dev/tty01` (COM2 in DOS).
A few words on the difference between `com`, `COM` and `tty`. For NetBSD, `com`
is the name of the serial port driver (the one that is displayed by `dmesg`) and
`tty` is the name of the port. Since numbering starts at 0, `com0` is the driver
for the first serial port, named `tty00`. In the DOS world, instead, `COM1`
refers to the first serial port (usually located at 0x3f8), `COM2` to the
second, and so on. Therefore `COM1` (DOS) corresponds to `/dev/tty00` (NetBSD).
Besides external modems connected to COM ports (using `/dev/tty0` on i386,
`/dev/tty[ab]` on sparc, ...) modems on USB (`/dev/ttyU*`) and pcmcia/cardbus
(`/dev/tty0`) can be used.
### Getting the connection information
The first thing to do is ask the provider the necessary information for the
connection, which means:
* The phone number of the nearest POP.
* The authentication method to be used.
* The username and password for the connection.
* The IP addresses of the name servers.
### resolv.conf and nsswitch.conf
The `/etc/resolv.conf` file must be configured using the information supplied by
the provider, especially the addresses of the DNS. In this example the two DNS
will be `126.96.36.199` and `188.8.131.52`:
And now an example of the `/etc/nsswitch.conf` file:
hosts: files dns
netgroup: files [notfound=return] nis
The defaults of doing hostname lookups via `/etc/hosts` followed by the DNS
works fine and there's usually no need to modify this.
### Creating the directories for pppd
The directories `/etc/ppp` and `/etc/ppp/peers` will contain the configuration
files for the PPP connection. After a fresh install of NetBSD they don't exist
and must be created (chmod 700).
# mkdir /etc/ppp
# mkdir /etc/ppp/peers
### Connection script and chat file
The connection script will be used as a parameter on the pppd command line; it
is located in `/etc/ppp/peers` and has usually the name of the provider. For
example, if the provider's name is BigNet and your user name for the connection
to the provider is alan, an example connection script could be:
connect '/usr/sbin/chat -v -f /etc/ppp/peers/bignet.chat'
In the previous example, the script specifies a *chat file* to be used for the
connection. The options in the script are detailed in the
If you are experiencing connection problems, add the following two lines to the
You will get a log of the operations performed when the system tries to connect.
The connection script calls the chat application to deal with the physical
connection (modem initialization, dialing, ...) The parameters to chat can be
specified inline in the connection script, but it is better to put them in a
separate file. If, for example, the telephone number of the POP to call is
`02 99999999`, an example chat script could be:
ABORT "NO CARRIER"
ABORT "NO DIALTONE"
*Note*: If you have problems with the chat file, you can try connecting manually
to the POP with the
[cu(1)](http://netbsd.gw.com/cgi-bin/man-cgi?cu+1+NetBSD-5.0.1+i386) program and
verify the exact strings that you are receiving.
During authentication each of the two systems verifies the identity of the other
system, although in practice you are not supposed to authenticate the provider,
but only to be verified by him, using one of the following methods:
Most providers use a PAP/CHAP authentication.
#### PAP/CHAP authentication
The authentication information (speak: password) is stored in the
`/etc/ppp/pap-secrets` for PAP and in `/etc/ppp/chap-secrets` for CHAP. The
lines have the following format:
user * password
alan * pZY9o
For security reasons the `pap-secrets` and `chap-secrets` files should be owned
by root and have permissions 600.
# chown root /etc/ppp/pap-secrets
# chown root /etc/ppp/chap-secrets
# chmod 600 /etc/ppp/pap-secrets
# chmod 600 /etc/ppp/chap-secrets
#### Login authentication
This type of authentication is not widely used today; if the provider uses login
authentication, user name and password must be supplied in the chat file instead
of the PAP/CHAP files, because the chat file simulates an interactive login. In
this case, set up appropriate permissions for the chat file.
The following is an example chat file with login authentication:
ABORT "NO CARRIER"
ABORT "NO DIALTONE"
### pppd options
The only thing left to do is the creation of the pppd options file, which is
`/etc/ppp/options` (chmod 644):
page for the meaning of the options.
### Testing the modem
Before activating the link it is a good idea to make a quick modem test, in
order to verify that the physical connection and the communication with the
modem works. For the test the
[cu(1)](http://netbsd.gw.com/cgi-bin/man-cgi?cu+1+NetBSD-5.0.1+i386) program can
be used, as in the following example.
1. Create the file `/etc/uucp/port` with the following lines:
(substitute the correct device in place of `/dev/tty01`).
2. Write the command `cu -p modem` to start sending commands to the modem. For
# cu -p modem
In the previous example the reset command (ATZ) was sent to the modem, which
replied with OK: the communication works. To exit
`~` (tilde) followed by `.` (dot), as in the example.
If the modem doesn't work, check that it is connected to the correct port (i.e.
you are using the right port with
[cu(1)](http://netbsd.gw.com/cgi-bin/man-cgi?cu+1+NetBSD-5.0.1+i386). Cables are
a frequent cause of trouble, too.
When you start
[cu(1)](http://netbsd.gw.com/cgi-bin/man-cgi?cu+1+NetBSD-5.0.1+i386) and a
message saying `Permission denied` appears, check who is the owner of the
`/dev/tty##` device, it must be "uucp". For example:
$ ls -l /dev/tty00
crw------- 1 uucp wheel 8, 0 Mar 22 20:39 /dev/tty00
If the owner is root, the following happens:
$ ls -l /dev/tty00
crw------- 1 root wheel 8, 0 Mar 22 20:39 /dev/tty00
$ cu -p modem
cu: open (/dev/tty00): Permission denied
cu: All matching ports in use
### Activating the link
At last everything is ready to connect to the provider with the following
# pppd call bignet
where `bignet` is the name of the already described connection script. To see
the connection messages of pppd, give the following command:
# tail -f /var/log/messages
To disconnect, do a **kill -HUP** of **pppd**.
# pkill -HUP pppd
### Using a script for connection and disconnection
When the connection works correctly, it's time to write a couple of scripts to
avoid repeating the commands every time. These two scripts can be named, for
example, `ppp-start` and `ppp-stop`.
`ppp-start` is used to connect to the provider:
if [ -f /var/spool/lock/LCK..$MODEM ]; then
echo ppp is already running...
pppd call $POP
tail -f /var/log/messages
`ppp-stop` is used to close the connection:
if [ -f /var/spool/lock/LCK..$MODEM ]; then
echo -f killing pppd...
kill -HUP `cat /var/spool/lock/LCK..$MODEM`
echo ppp is not active
The two scripts take advantage of the fact that when pppd is active, it creates
the file `LCK..tty01` in the `/var/spool/lock` directory. This file contains the
process ID (*pid*) of the pppd process.
The two scripts must be executable:
# chmod u+x ppp-start ppp-stop
### Running commands after dialin
If you find yourself to always run the same set of commands each time you dial
in, you can put them in a script `/etc/ppp/ip-up` which will be called by
successful dial-in. Likewise, before the connection is closed down,
`/etc/ppp/ip-down` is executed. Both scripts are expected to be executable. See
## Creating a small home network
Networking is one of the main strengths of Unix and NetBSD is no exception:
networking is both powerful and easy to set up and inexpensive too, because
there is no need to buy additional software to communicate or to build a server.
[[Setting up an Internet gateway with IPNAT|guide/net-practice#ipnat]] explains
how to configure a NetBSD machine to act as a gateway for a network: with IPNAT
all the hosts of the network can reach the Internet with a single connection to
a provider made by the gateway machine. The only thing to be checked before
creating the network is to buy network cards supported by NetBSD (check the
`INSTALL.*` files for a list of supported devices).
First, the network cards must be installed and connected to a hub, switch or
directly (see the next image for an example configuration).
Next, check that the network cards are recognized by the kernel, studying the
output of the `dmesg` command. In the following example the kernel recognized
correctly an NE2000 clone:
ne0 at isa0 port 0x280-0x29f irq 9
ne0: NE2000 Ethernet
ne0: Ethernet address 00:c2:dd:c1:d1:21
If the card is not recognized by the kernel, check that it is enabled in the
kernel configuration file and then that the card's IRQ matches the one that the
kernel expects. For example, this is the isa NE2000 line in the configuration
file; the kernel expects the card to be at IRQ 9.
ne0 at isa? port 0x280 irq 9 # NE000 ethernet cards
If the card's configuration is different, it will probably not be found at boot.
In this case, either change the line in the kernel configuration file and
compile a new kernel or change the card's setup (usually through a setup disk
or, for old cards, a jumper on the card).
The following command shows the network card's current configuration:
# ifconfig ne0
ne0: flags=8822<BROADCAST,NOTRAILERS,SIMPLEX,MULTICAST> mtu 1500
media: Ethernet autoselect (10baseT)
inet6 fe80::250:baff:feaa:a77f%ne0 prefixlen 64 scopeid 0x1
The software configuration of the network card is very easy. The IP address
192.168.1.1 is assigned to the card.
# ifconfig ne0 inet 192.168.1.1 netmask 0xffffff00
Note that the networks 10.0.0.0/8 and 192.168.0.0/16 are reserved for private
networks, which is what we're setting up here.
Repeating the previous command now gives a different result:
# ifconfig ne0
ne0: flags=8863<UP,BROADCAST,NOTRAILERS,RUNNING,SIMPLEX,MULTICAST> mtu 1500
media: Ethernet autoselect (10baseT)
inet 192.168.1.1 netmask 0xffffff00 broadcast 192.168.1.255
inet6 fe80::250:baff:feaa:a77f%ne0 prefixlen 64 scopeid 0x1
The output of `ifconfig` has now changed: the IP address is now printed and
there are two new flags, `UP` and `RUNNING` If the interface isn't `UP`, it will
not be used by the system to send packets.
The host was given the IP address 192.168.1.1, which belongs to the set of
addresses reserved for internal networks which are not reachable from the
Internet. The configuration is finished and must now be tested; if there is
another active host on the network, a `ping` can be tried. For example, if
192.168.1.2 is the address of the active host:
# ping 192.168.1.2
PING ape (192.168.1.2): 56 data bytes
64 bytes from 192.168.1.2: icmp_seq=0 ttl=255 time=1.286 ms
64 bytes from 192.168.1.2: icmp_seq=1 ttl=255 time=0.649 ms
64 bytes from 192.168.1.2: icmp_seq=2 ttl=255 time=0.681 ms
64 bytes from 192.168.1.2: icmp_seq=3 ttl=255 time=0.656 ms
----ape PING Statistics----
4 packets transmitted, 4 packets received, 0.0% packet loss
round-trip min/avg/max/stddev = 0.649/0.818/1.286/0.312 ms
With the current setup, at the next boot it will be necessary to repeat the
configuration of the network card. In order to avoid repeating the card's
configuration at each boot, add the following lines to `/etc/rc.conf`:
ifconfig_ne0="inet 192.168.1.1 netmask 0xffffff00"
In this example the variable `ifconfig_ne0` was set because the network card was
recognized as *ne0* by the kernel; if you are using a different adapter,
substitute the appropriate name in place of ne0.
At the next boot the network card will be configured automatically.
If you have a router that is connected to the internet, you can use it as
default router, which will handle all your packets. To do so, set `defaultroute`
to the router's IP address in `/etc/rc.conf`:
Be sure to use the default router's IP address instead of name, in case your DNS
server is beyond the default router. In that case, the DNS server couldn't be
reached to resolve the default router's hostname and vice versa, creating a
To reach hosts on your local network, and assuming you really have very few
hosts, adjust `/etc/hosts` to contain the addresses of all the hosts belonging
to the internal network. For example:
# Host Database
# This file should contain the addresses and aliases
# for local hosts that share this file.
# It is used only for "ifconfig" and other operations
# before the nameserver is started.
# RFC 1918 specifies that these networks are "internal".
# 10.0.0.0 10.255.255.255
# 172.16.0.0 172.31.255.255
# 192.168.0.0 192.168.255.255
192.168.1.1 ape.insetti.net ape
192.168.1.2 vespa.insetti.net vespa
If you are dialed in via an Internet Service Provider, or if you have a local
Domain Name Server (DNS) running, you may want to use it to resolve hostnames to
IP addresses, possibly in addition to `/etc/hosts`, which would only know your
own hosts. To configure a machine as DNS client, you need to edit
`/etc/resolv.conf`, and enter the DNS server's address, in addition to an
optional domain name that will be appended to hosts with no domain, in order to
create a FQDN for resolving. Assuming your DNS server's IP address is
192.168.1.2 and it is setup to serve for "home.net", put the following into
The `/etc/nsswitch.conf` file should be checked as explained in the previous
Summing up, to configure the network the following must be done: the network
adapters must be installed and physically connected. Next they must be
configured (with **ifconfig**) and, finally, the file `/etc/rc.conf` must be
modified to configure the interface and possibly default router, and
`/etc/resolv.conf` and `/etc/nsswitch.conf` should be adjusted if DNS should be
used. This type of network management is sufficient for small networks without
## Setting up an Internet gateway with IPNAT
The mysterious acronym IPNAT hides the Internet Protocol Network Address
Translation, which enables the routing of an internal network (e.g. your home
network as described in the previous section) on a real network (Internet). This
means that with only one *real* IP, static or dynamic, belonging to a gateway
running IPNAT, it is possible to create simultaneous connections to the Internet
for all the hosts of the internal network.
Some usage examples of IPNAT can be found in the subdirectory
`/usr/share/examples/ipf`: look at the files `BASIC.NAT` and `nat-setup`.
The setup for the example described in this section is detailed in the following
figure: *host 1* can connect to the Internet calling a provider with a modem and
getting a dynamic IP address. *host 2* and *host 3* can't communicate with the
Internet with a normal setup: IPNAT allows them to do it: host 1 will act as a
Internet gateway for hosts 2 and 3. Using host 1 as default router, hosts 2 and
3 will be able to access the Internet.
![Network with gateway](/guide/images/net1.gif)
**Network with gateway**
### Configuring the gateway/firewall
To use IPNAT, the *pseudo-device ipfilter* must be compiled into the kernel, and
IP packet forwarding must be enabled in the kernel. To check, run:
# sysctl net.inet.ip.forwarding
net.inet.ip.forwarding = 1
If the result is `1` as in the previous example, the option is enabled,
otherwise, if the result is `0` the option is disabled. You can do two things:
1. Compile a new kernel, with the GATEWAY option enabled.
2. Enable the option in the current kernel with the following command:
# sysctl -w net.inet.ip.forwarding=1
You can add sysctl settings to `/etc/sysctl.conf` to have them set
automatically at boot. In this case you would want to add
The rest of this section explains how to create an IPNAT configuration that is
automatically started every time that a connection to the provider is activated
with the PPP link. With this configuration all the host of a home network (for
example) will be able to connect to the Internet through the gateway machine,
even if they don't use NetBSD.
For the setup, first, create the `/etc/ipnat.conf` file containing the following
map ppp0 192.168.1.0/24 -> 0/32 proxy port ftp ftp/tcp
map ppp0 192.168.1.0/24 -> 0/32 portmap tcp/udp 40000:60000
map ppp0 192.168.1.0/24 -> 0/32
192.168.1.0/24 are the network addresses that should be mapped. The first line
of the configuration file is optional: it enables active FTP to work through the
gateway. The second line is used to handle correctly tcp and udp packets; the
portmapping is necessary because of the many to one relationship). The third
line is used to enable ICMP, ping, etc.
Next, create the `/etc/ppp/ip-up` file; it will be called automatically every
time that the PPP link is activated:
Create the file `/etc/ppp/ip-down`; it will be called automatically when the PPP
link is closed:
Both `ip-up` and `ip-down` must be executable:
# chmod u+x ip-up ip-down
The gateway machine is now ready.
### Configuring the clients
Create a `/etc/resolv.conf` file like the one on the gateway machine, to make
the clients access the same DNS server as the gateway.
Next, make all clients use the gateway as their default router. Use the
# route add default 192.168.1.1
192.168.1.1 is the address of the gateway machine configured in the previous
Of course you don't want to give this command every time, so it's better to
define the `defaultroute` entry in the `/etc/rc.conf` file: the default route
will be set automatically during system initialization, using the defaultroute
option as an argument to the **route add default** command.
If the client machine is not using NetBSD, the configuration will be different.
On Windows PCs you need to set the gateway property of the TCP/IP protocol to
the IP address of the NetBSD gateway.
That's all that needs to be done on the client machines.
### Some useful commands
The following commands can be useful for diagnosing problems:
* `ping` -- tries to connect to other computers via ICMP (usually used for
testing if a connection exists).
* `netstat -r` -- Displays the routing tables (similar to **route show**).
* `traceroute` -- On the client it shows the route followed by the packets to
* `tcpdump` -- Use on the gateway to monitor TCP/IP traffic.
## Setting up a network bridge device
A bridge can be used to combine different physical networks into one logical
network, i.e. connect them at layer 2 of the ISO-OSI model, not at layer 3,
which is what a router would do. The NetBSD `bridge` driver provides bridge
functionality on NetBSD systems.
### Bridge example
In this example two physical networks are going to be combined in one logical
network, 192.168.1.0, using a NetBSD bridge. The NetBSD machine which is going
to act as bridge has two interfaces, ne0 and ne1, which are each connected to
one physical network.
The first step is to make sure support for the `bridge` is compiled in the
running kernel. Support is included in the GENERIC kernel.
When the system is ready the bridge can be created, this can be done using the
command. First of a bridge interface has to be created. With the following
`ifconfig` command the `bridge0` interface will be created:
$ ifconfig bridge0 create
Please make sure that at this point both the ne0 and ne1 interfaces are up. The
next step is to add the ne0 and ne1 interfaces to the bridge.
$ brconfig bridge0 add ne0 add ne1 up
This configuration can be automatically set up by creating an
`/etc/ifconfig.interface` file, in this case `/etc/ifconfig.bridge0`, with the
!brconfig $int add ne0 add ne1 up
After setting up the bridge the bridge configuration can be displayed using the
`brconfig -a` command. Remember that if you want to give the bridge machine an
IP address you can only allocate an IP address to one of the interfaces which
are part of the bridge.
## A common LAN setup
The small home network discussed in the previous section contained many items
that were configured manually. In bigger LANs that are centrally managed, one
can expect Internet connectivity being available via some router, a DNS server
being available, and most important, a DHCP server which hands out IP addresses
to clients on request. To make a NetBSD client run in such an environment, it's
usually enough to set
in `/etc/rc.conf`, and the IP address will be set automatically,
`/etc/resolv.conf` will be created and routing setup to the default router.
## Connecting two PCs through a serial line
If you need to transfer files between two PCs which are not networked there is a
simple solution which is particularly handy when copying the files to a floppy
is not practical: the two machines can be networked with a serial cable (a *null
modem* cable). The following sections describe some configurations.
### Connecting NetBSD with BSD or Linux
The easiest case is when both machines run NetBSD: making a connection with the
SLIP protocol is very easy. On the first machine write the following commands:
# slattach /dev/tty00
# ifconfig sl0 inet 192.168.1.1 192.168.1.2
On the second machine write the following commands:
# slattach /dev/tty00
# ifconfig sl0 inet 192.168.1.2 192.168.1.1
Now you can test the connection with `ping`; for example, on the second PC
# ping 192.168.1.1
If everything worked there is now an active network connection between the two
machines and ftp, telnet and other similar commands can be executed. The textual
aliases of the machines can be written in the `/etc/hosts` file.
* In the previous example both PCs used the first serial port (`/dev/tty0`).
Substitute the appropriate device if you are using another port.
* IP addresses like 192.168.x.x are reserved for `internal` networks. The first
PC has address 192.168.1.1 and the second 192.168.1.2.
* To achieve a faster connection the `-s speed` option to `slattach` can be
* `ftp` can be used to transfer files only if inetd is active and the ftpd
* server is enabled.
If one of the two PCs runs Linux, the commands are slightly different (on the
Linux machine only). If the Linux machine gets the 192.168.1.2 address, the
following commands are needed:
# slattach -p slip -s 115200 /dev/ttyS0 &
# ifconfig sl0 192.168.1.2 pointopoint 192.168.1.1 up
# route add 192.168.1.1 dev sl0
Don't forget the `&` in the first command.
### Connecting NetBSD and Windows NT
NetBSD and Windows NT can be (almost) easily networked with a serial *null
modem* cable. Basically what needs to be done is to create a *Remote Access*
connection under Windows NT and to start pppd on NetBSD.
Start pppd as root after having created a `.ppprc` in `/root`. Use the following
example as a template.
connect '/usr/sbin/chat -v CLIENT CLIENTSERVER'
The meaning of the first line will be explained later in this section;
192.168.1.2 is the IP address that will be assigned by NetBSD to the Windows NT
host; `tty00` is the serial port used for the connection (first serial port).
On the NT side a *null modem* device must be installed from the Control Panel
(Modem icon) and a Remote Access connection using this modem must be created.
The null modem driver is standard under Windows NT 4 but it's not a 100% null
modem: when the link is activated, NT sends the string CLIENT and expects to
receive the answer CLIENTSERVER. This is the meaning of the first line of the
`.ppprc` file: `chat` must answer to NT when the connection is activated or
the connection will fail.
In the configuration of the Remote Access connection the following must be
specified: use the null modem, telephone number `1` (it's not used, anyway), PPP
server, enable only TCP/IP protocol, use IP address and nameservers from the
server (NetBSD in this case). Select the hardware control flow and set the port
to 115200 8N1.
Now everything is ready to activate the connection.
* Connect the serial ports of the two machines with the null modem cable.
* Launch pppd on NetBSD. To see the messages of pppd:
`tail -f /var/log/messages`).
* Activate the Remote Access connection on Windows NT.
### Connecting NetBSD and Windows 95
The setup for Windows 95 is similar to the one for Windows NT: Remote Access on
Windows 95 and the PPP server on NetBSD will be used. Most (if not all) Windows
95 releases don't have the *null modem* driver, which makes things a little more
complicated. The easiest solution is to find one of the available null modem
drivers on the Internet (it's a small `.INF` file) and repeat the same steps as
for Windows NT. The only difference is that the first line of the `.ppprc` file
(the one that calls `chat`) can be removed.
If you can't find a real null modem driver for Windows 95 it's still possible to
use a little trick:
* Create a Remote Access connection like the one described before for Windows
NT, but using the *Standard Modem*.
* In `.ppprc` substitute the line that calls **chat** with the following line
connect '/usr/sbin/chat -v ATH OK AT OK ATE0V1 OK AT OK ATDT CONNECT'
* Activate the connection as described in the section before for Windows NT.
In this way the `chat` program, called when the connection is activated,
emulates what Windows 95 thinks is a standard modem, returning to Windows 95 the
same answers that a standard modem would return. Whenever Windows 95 sends a
modem command string, `chat` returns OK.
## IPv6 Connectivity & Transition via 6to4
This section will concentrate on how to get network connectivity for IPv6 and -
as that is rarely available directly - talk at length about the alternatives to
native IPv6 connectivity as a transitional method until native IPv6 peers are
Finding an ISP that offers IPv6 natively needs quite some luck. What you need
next is a router that will be able to handle the traffic. To date, not all
router manufacturers offer IPv6 or hardware accelerated IPv6 features, and
gateway NAT boxes only rarely support IPv6 and also block IPv6 tunnels. An
alternative approach involves configuring a standard PC running NetBSD to act as
a router. The base NetBSD system contains a complete IPv6 routing solution, and
for special routing needs software like Zebra can provide additional routing
protocols. This solution is rather common for sites that want IPv6
connectivity today. The drawbacks are that you need an ISP that supports
IPv6 and that you may need a dedicated uplink only for IPv6.
IPv6 to-the-door may be rare, but you can still get IPv6 connectivity by using
tunnels. Instead of talking IPv6 on the wire, the IPv6 packets are encapsulated
in IPv4 packets, as shown in the next image. Using the existing IPv4
infrastructure, the encapsulated packets are sent to a IPv6-capable uplink that
will then remove the encapsulation, and forward the IPv6 packets.
![A frequently used method for transition is tunneling IPv6 in IPv4 packets](/guide/images/ipv6-en-2tunnel.gif)
**A frequently used method for transition is tunneling IPv6 in IPv4 packets**
When using tunnels, there are two possibilities. One is to use a so-called
*configured* tunnel, the other is called an *automatic* tunnel. A *configured*
tunnel is one that required preparation from both ends of the tunnel, usually
connected with some kind of registration to exchange setup information. An
example for such a configured tunnel is the IPv6-over-IPv4 encapsulation
[RFC1933](http://tools.ietf.org/html/rfc1933) ("RFC 1933: Transition Mechanisms
for IPv6 Hosts and Routers"), and that's implemented e.g. by the
device found in NetBSD.
An *automatic* tunnel consists of a public server that has some kind of IPv6
connectivity, e.g. via 6Bone. That server has made its connectivity data public,
and also runs a tunneling protocol that does not require an explicit
registration of the sites using it as uplink. A well-used example of such a
protocol is the 6to4 mechanism described in
[RFC3056](http://tools.ietf.org/html/rfc3056) ("RFC 3056: Connection of IPv6
Domains via IPv4 Clouds"), and that is implemented in the
found in NetBSD's. Another mechanism that does not require registration of
IPv6-information is the 6over4 mechanism, which implements transporting of IPv6
over a multicast-enabled IPv4 network, instead of e.g. ethernet or FDDI. 6over4
is documented in [RFC2529](http://tools.ietf.org/html/rfc2529) ("RFC 2529:
Transmission of IPv6 over IPv4 Domains without Explicit Tunnels"). It's main
drawback is that you do need existing multicast infrastructure. If you don't
have that, setting it up is about as much effort as setting up a configured IPv6
tunnel directly, so it's usually not worth bothering in that case.
### Getting 6to4 IPv6 up & running
6to4 is an easy way to get IPv6 connectivity for hosts that only have an IPv4
uplink, especially if you have the background given in
[[the chapter about IPv6|guide/net-intro#ipv6-intro]]. It can be used with
static as well as dynamically assigned IPv4 addresses, e.g. as found in modem
dialup scenarios today. When using dynamic IPv4 addresses, a change of IP
addresses will be a problem for incoming traffic, i.e. you can't run persistent
Example configurations given in this section are for NetBSD 1.5.2.
### Obtaining IPv6 Address Space for 6to4
The 6to4 IPv6 setup on your side doesn't consist of a single IPv6 address;
Instead, you get a whole /48 network! The IPv6 addresses are derived from your
(single) IPv4 address. The address prefix *2002:` is reserved for 6to4 based
addresses (i.e. IPv6 addresses derived from IPv4 addresses). The next 32 bits
are your IPv4 address. This results in a /48 network that you can use for your
very own purpose. It leaves 16 bits space for 2^16^ IPv6 subnets, which can take
up to 2^64^ nodes each. The next figure illustrates the building of your IPv6
address (range) from your IPv4 address.
Thanks to the 6to4 prefix and your worldwide unique IPv4 address, this address
block is unique, and it's mapped to your machine carrying the IPv4 address in
![6to4 derives an IPv6 from an IPv4 address](/guide/images/ipv6-en-3adr.gif)
**6to4 derives an IPv6 from an IPv4 address**
### How to get connected
In contrast to the configured *IPv6-over-IPv4 tunnel* setup, you do not have to
register at a 6bone-gateway, which would only then forward your IPv6 traffic
encapsulated in IPv4. Instead, as your IPv6 address is derived from your IPv4
address, inbound traffic can be sent through the nearest 6to4 relay router.
De-encapsulation of the packet is done via a 6to4-capable network interface,
which then forwards the resulting IPv6 packet according to your routing setup
(in case you have more than one machine connected on your 6to4 assigned
To transmit IPv6 packets, the 6to4 router will encapsulate them inside IPv4
packets; a system performing these functions is called a 6to4 border router.
These packets have a default route to the *6to4 relay anycast prefix*. This
anycast prefix will route the tunnel to a *6to4 relay router*.
![Request and reply can be routed via different gateways in 6to4](/guide/images/ipv6-en-1scene.gif)
**Request and reply can be routed via different gateways in 6to4**
### Security Considerations
In contrast to the *configured tunnel* setup, you usually can't setup packet
filters to block 6to4-packets from unauthorized sources, as this is exactly how
(and why) 6to4 works at all. As such, malicious users can send packets with
invalid/hazardous IPv6 payload. If you don't already filter on your border
gateways anyways, packets with the following characteristics should not be
allowed as valid 6to4 packets, and some firewalling seems to be justified for
* unspecified IPv4 source/destination address: 0.0.0.0/8
* loopback address in outer (v4) source/destination: 127.0.0.0/8
* IPv4 multicast in source/destination: 184.108.40.206/4
* limited broadcasts: 255.0.0.0/8
* subnet broadcast address as source/destination: depends on your IPv4 setup
page documents some common configuration mistakes intercepted by default by the
KAME stack as well as some further advice on filtering, but keep in mind that
because of the requirement of these filters, 6to4 is not perfectly secure.
Still, if forged 6to4 packets become a problem, you can use IPsec authentication
to ensure the IPv6 packets are not modified.
### Data Needed for 6to4 Setup
In order to setup and configure IPv6 over 6to4, a few bits of configuration data
must be known in advance. These are:
* Your local IPv4 address. It can be determined using either the `ifconfig -a`
or `netstat -i` commands on most Unix systems. If you use a NATing gateway or
something, be sure to use the official, outside-visible address, not your
private (10/8 or 192.168/16) one.
We will use 220.127.116.11 as the local IPv4 address in our example.
* Your local IPv6 address, as derived from the IPv4 address. See the previous
figure ("6to4 derives an IPv6 from an IPv4 address") about how to do so.
For our example, this is 2002:3ee0:3972:0001::1 (18.104.22.168 == 0x3ee03972,
0001::1 arbitrarily chosen).
* The *6to4 IPv6 relay anycast address*. which is 2002:c058:6301::, or the IPv6
address of a specific 6to4 relay router you want to use. The IPv6 address
will do, as it also contains the IPv4 address in the usual 6to4 translation.
### Kernel Preparation
To process 6to4 packets, the operating system kernel needs to know about them.
For that a driver has to be compiled in that knows about 6to4, and how to handle
it. In NetBSD 4.0 and newer, the driver is already present in GENERIC kernel
configurations, so the procedure below is usually unnecessary.
For a NetBSD kernel, put the following into your kernel config file to prepare
it for using IPv6 and 6to4, e.g. on NetBSD use:
options INET6 # IPv6
pseudo-device stf # 6to4 IPv6 over IPv4 encapsulation
Note that the
[stf(4)](http://netbsd.gw.com/cgi-bin/man-cgi?stf+4+NetBSD-5.0.1+i386) device is
not enabled by default on NetBSD releases older than 4.0. Rebuild your kernel,
then reboot your system to use the new kernel. Please consult
[[Compiling the kernel|guide/kernel]] for further information on configuring,
building and installing a new kernel!
### 6to4 Setup
This section describes the commands to setup 6to4. In short, the steps performed
1. Configure interface
2. Set default route
3. Setup Router Advertisement, if wanted
The first step in setting up 6to4 is creating the 6to4 interface and assigning
an IPv6 address to it. This is achieved with the
command. Assuming the example configuration above, the commands for NetBSD are:
# ifconfig stf0 create
# ifconfig stf0 inet6 2002:3ee0:3972:1::1 prefixlen 16 alias
After configuring the 6to4 device with these commands, routing needs to be
setup, to forward all tunneled IPv6 traffic to the 6to4 relay router. The best
way to do this is by setting a default route, the command to do so is, for
# route add -inet6 default 2002:c058:6301::
Note that NetBSD's
determines the IPv4 address of the 6to4 uplink from the routing table. Using
this feature, it is easy to setup your own 6to4 (uplink) gateway if you have an
IPv6 uplink, e.g. via 6Bone.
After these commands, you are connected to the IPv6-enabled world -
Congratulations! Assuming name resolution is still done via IPv4, you can now
ping an IPv6-site like www.kame.net or www6.NetBSD.org:
# /sbin/ping6 www.kame.net
As a final step in setting up IPv6 via 6to4, you will want to setup Router
Advertisement if you have several hosts on your network. While it is possible to
setup 6to4 on each node, doing so will result in very expensive routing from one
node to the other - packets will be sent to the remote 6to4 gateway, which will
then route the packets back to the neighbor node. Instead, setting up 6to4 on
one machine and talking native IPv6 on-wire is the preferred method of handling
The first step to do so is to assign an IPv6-address to your ethernet. In the
following example we will assume subnet `2` of the IPv6-net is used for the
local ethernet and the MAC address of the ethernet interface is
12:34:56:78:9a:bc, i.e. your local gateway's ethernet interface's IP address
will be 2002:3ee0:3972:2:1234:56ff:fe78:9abc. Assign this address to your
ethernet interface, e.g.
# ifconfig ne0 inet6 alias 2002:3ee0:3972:2:1234:56ff:fe78:9abc
Here, `ne0` is an example for your ethernet card interface. This will most
likely be different for your setup, depending on what kind of card is used.
Next thing that needs to be ensured for setting up the router is that it will
actually forward packets from the local 6to4 device to the ethernet device and
back. To enable IPv6 packet forwarding, set `ip6mode=router` in NetBSD's
`/etc/rc.conf`, which will result in the `net.inet6.ip6.forwarding` sysctl being
set to `1`:
# sysctl -w net.inet6.ip6.forwarding=1
![Enabling packet forwarding is needed for a 6to4 router](/guide/images/ipv6-en-5forward.gif)
**Enabling packet forwarding is needed for a 6to4 router**
To setup router advertisement on BSD, the file `/etc/rtadvd.conf` needs to be
checked. It allows configuration of many things, but usually the default config
of not containing any data is ok. With that default, IPv6 addresses found on all
of the router's network interfaces will be advertised.
After checking the router advertisement configuration is correct and IPv6
forwarding is turned on, the daemon handling it can be started. Under NetBSD, it
is called `rtadvd`. Start it up either manually (for testing it the first time)
or via the system's startup scripts, and see all your local nodes automagically
configure the advertised subnet address in addition to their already-existing
link local address.
### Quickstart using pkgsrc/net/hf6to4
So far, we have described how 6to4 works and how to set it up manually. For an
automated way to make everything happen e.g. when going online, the 'hf6to4'
package is convenient. It will determine your IPv6 address from the IPv4 address
you got assigned by your provider, then set things up that you are connected.
Steps to setup the pkgsrc/net/hf6to4 package are:
1. Install the package either by compiling it from pkgsrc, or by `pkg_add`'ing
the 6to4-1.2 package.
# cd /usr/pkgsrc/net/hf6to4
# make install
2. Make sure you have the
pseudo-device in your kernel, see above.
3. Configure the 'hf6to4' package. First, copy
`/usr/pkg/share/examples/hf6to4/hf6to4.conf` to `/usr/pkg/etc/hf6to4.conf`,
then adjust the variables. Note that the file is in /bin/sh syntax.
# cd /usr/pkg/etc
# cp ../share/examples/hf6to4/hf6to4.conf hf6to4.conf
# vi hf6to4.conf
Please see the
manpage for an explanation of all the variables you can set in
`hf6to4.conf`. If you have dialup IP via PPP, and don't want to run Router
Advertizing for other IPv6 machines on your home or office network, you
don't need to configure anything. If you want to setup Router Advertising,
you need to set the `in_if` to the internal (ethernet) interface, e.g.
$in_if="rtk0"; # Inside (ethernet) interface
4. Now dial up, then start the 6to4 command manually:
# /usr/pkg/sbin/hf6to4 start
5. After that, you should be connected, use
see if everything works:
# ping6 www.NetBSD.org
PING6(56=40+8+8 bytes) 2002:d954:110b:1::1 --> 2001:4f8:4:7:2e0:81ff:fe52:9a6b
16 bytes from 2001:4f8:4:7:2e0:81ff:fe52:9a6b, icmp_seq=0 hlim=60 time=250.234 ms
16 bytes from 2001:4f8:4:7:2e0:81ff:fe52:9a6b, icmp_seq=1 hlim=60 time=255.652 ms
16 bytes from 2001:4f8:4:7:2e0:81ff:fe52:9a6b, icmp_seq=2 hlim=60 time=251.237 ms
--- www.NetBSD.org ping6 statistics ---
3 packets transmitted, 3 packets received, 0.0% packet loss
round-trip min/avg/max/std-dev = 250.234/252.374/255.652/2.354 ms
# traceroute6 www.NetBSD.org
traceroute6 to www.NetBSD.org (2001:4f8:4:7:2e0:81ff:fe52:9a6b)
from 2002:d954:110b:1::1, 64 hops max, 12 byte packets
1 2002:c25f:6cbf:1::1 66.31 ms 66.382 ms 69.062 ms
2 nr-erl1.6win.dfn.de 76.134 ms * 76.87 ms
3 nr-fra1.6win.dfn.de 76.371 ms 80.709 ms 79.482 ms
4 dfn.de6.de.6net.org 92.763 ms 90.863 ms 94.322 ms
5 de.nl6.nl.6net.org 116.115 ms 93.463 ms 96.331 ms
6 nl.uk6.uk.6net.org 103.347 ms 99.334 ms 100.803 ms
7 uk1.uk61.uk.6net.org 99.481 ms 100.421 ms 100.119 ms
8 2001:798:28:300::2 89.711 ms 90.435 ms 90.035 ms
9 ge-1-0-0-2.r20.londen03.uk.bb.verio.net 179.671 ms 185.141 ms 185.86 ms
10 p16-0-0-0.r81.nycmny01.us.bb.verio.net 177.067 ms 179.086 ms 178.05 ms
11 p16-1-1-3.r20.nycmny01.us.bb.verio.net 178.04 ms 179.727 ms 184.165 ms
12 p16-0-1-1.r20.mlpsca01.us.bb.verio.net 249.856 ms 247.476 ms 249.012 ms
13 p64-0-0-0.r21.snjsca04.us.bb.verio.net 239.691 ms 241.404 ms 240.998 ms
14 p64-0-0-0.r21.plalca01.us.bb.verio.net 247.541 ms 246.661 ms 246.359 ms
15 xe-0-2-0.r20.plalca01.us.bb.verio.net 240.987 ms 239.056 ms 241.251 ms
16 ge-6-1.a01.snfcca05.us.ra.verio.net 240.868 ms 241.29 ms 242.337 ms
17 fa-5-2.a01.snfcca05.us.ce.verio.net 249.477 ms 250.4 ms 256.035 ms
18 2001:4f8:4:7:2e0:81ff:fe52:9a6b 268.164 ms 252.97 ms 252.366 ms
Please note that `traceroute6` shows the v6 hops only, any underlying
tunnels are invisible and thus not displayed.
6. If this works, you can put the following lines into your `/etc/ppp/ip-up`
script to run the command each time you go online:
logger -p user.info -t ip-up Configuring 6to4 IPv6
7. If you want to route IPv6 for your LAN, you can instruct `6to4.pl` to setup
Router Advertising for you too:
# /usr/pkg/sbin/hf6to4 rtadvd-start
You can put that command into `/etc/ppp/ip-up` as well to make it permanent.
8. If you have changed `/etc/ppp/ip-up` to setup 6to4 automatically, you will
most likely want to change `/etc/ppp/ip-down` too, to shut it down when you
go offline. Here's what to put into `/etc/ppp/ip-down`:
logger -p user.info -t ip-down Shutting down 6to4 IPv6
### Known 6to4 Relay Routers
It is normally not necessary to pick a specific 6to4 relay router, but if
necessary, you may find a list of known working routers at
[http://www.kfu.com/\~nsayer/6to4/](http://www.kfu.com/~nsayer/6to4/). In tests,
only 6to4.kfu.com and 6to4.ipv6.microsoft.com were found working. Cisco has one
that requires registration, see
There's also an experimental 6to4 server located in Germany,
6to4.ipv6.fh-regensburg.de. This server runs under NetBSD 1.6 and was setup
using the configuration steps described above. The whole configuration of the
machine can be seen at
### Tunneling 6to4 through an IPFilter firewall
The 6to4 protocol encapsulates IPv6 packets in IPv4, and gives them their own IP
type, which most firewalls block as unknown, as their payload type is directly
`TCP`, `UDP` or `ICMP`. Usually, you want to setup your 6to4 gateway on the same
machine that is directly connected to the (IPv4) internet, and which usually
runs the firewall. For the case that you want to run your 6to4 gateway behind a
firewall, you need to drill a hole into the firewall, to let 6to4 packets
through. Here is how to do this!
The example assumes that you use the `ppp0` interface on your firewall to
connect to the Internet.
Put the following lines into `/etc/ipf.conf` to allow your IPFilter firewall let
all 6to4 packets pass (lines broken with `\` due to space restrictions; please
put them lines continued that way all in one line):
# Handle traffic by different rulesets
block in quick on ppp0 all head 1
block out quick on ppp0 all head 2
### Incoming packets:
# allow some IPv4:
pass in log quick on ppp0 proto tcp from any to any \
port = www flags S keep state keep frags group 1
pass in quick on ppp0 proto tcp from any to any \
port = ssh keep state group 1
pass in quick on ppp0 proto tcp from any to any \
port = mail keep state group 1
pass in log quick on ppp0 proto tcp from any to any \
port = ftp keep state group 1
pass in log quick on ppp0 proto tcp from any to any \
port = ftp-data keep state group 1
pass in log quick on ppp0 proto icmp from any to any group 1
# allow all IPv6:
pass in quick on ppp0 proto ipv6 from any to any group 1
pass in log quick on ppp0 proto ipv6-route from any to any group 1
pass in log quick on ppp0 proto ipv6-frag from any to any group 1
pass in log quick on ppp0 proto ipv6-icmp from any to any group 1
pass in log quick on ppp0 proto ipv6-nonxt from any to any group 1
pass in log quick on ppp0 proto ipv6-opts from any to any group 1
# block rest:
blockin log quick on ppp0 all group 1
### Outgoing packets:
# allow usual stuff:
pass out quick on ppp0 proto tcp from any to any flags S \
keep state keep frags group 2
pass out quick on ppp0 proto udp from any to any \
keep state keep frags group 2
pass out quick on ppp0 proto icmp from any to any \
keep state group 2
# allow all IPv6:
pass out quick on ppp0 proto ipv6 from any to any group 2
pass out log quick on ppp0 proto ipv6-route from any to any group 2
pass out log quick on ppp0 proto ipv6-frag from any to any group 2
pass out log quick on ppp0 proto ipv6-icmp from any to any group 2
pass out log quick on ppp0 proto ipv6-nonxt from any to any group 2
pass out log quick on ppp0 proto ipv6-opts from any to any group 2
# block rest:
block out log quick on ppp0 all group 2
Now any host on your network can send (the `out` rules) and receive (the `in`
rules) v4-encapsulated IPv6 packets, allowing setup of any of them as a 6to4
gateway. Of course you only want to do this on one host and use native IPv6
between your hosts, and you may also want to enforce this with more restrictive
rulesets, please see
for more information on IPFilter rules.
After your firewall lets pass encapsulated IPv6 packets, you may want to set up
your 6to4 gateway to monitor the IPv6 traffic, or even restrict it. To do so,
you need to setup IPFilter on your 6to4 gateway as well. For basic monitoring,
enable `ipfilter=yes` in `/etc/rc.conf` and put the following into
pass in log quick on stf0 from any to any
pass out log quick on stf0 from any to any
This logs all (IPv6) traffic going in and out of your `stf0` tunneling
interface. You can add filter rules as well if needed.
If you are more interested in traffic stats than a general overview of your
network traffic, using MRTG in conjunction with the `net-snmp` package is
recommended instead of analyzing IPFilter log files.
### Conclusion & Further Reading
Compared to where IPv4 is today, IPv6 is still in its early steps. It is
working, there are all sort of services and clients available, only the userbase
is missing. It is hoped the information provided here helps people better
understand what IPv6 is, and to start playing with it.
A few links should be mentioned here for interested parties:
* An example script to setup 6to4 on BSD based machines is available at
<http://www.NetBSD.org/packages/net/hf6to4/>. The script determines your IPv6
address and sets up 6to4 and (if wanted) router advertising. It was designed
to work in dialup setups with changing IPv4 addresses.
* Given that there isn't a standard for IPv6 in Linux land today, there are
different setup instructions for most distributions. The setup of IPv6 on
Debian GNU/Linux can be found at
* The BSD Unix implementations have their own IPv6 documentation each,
interesting URLs are <http://www.NetBSD.org/docs/network/ipv6/> for NetBSD,
* Projects working on implementing IPv6 protocol stacks for free Unix like
operating systems are KAME for BSD and USAGI for Linux. Their web sites can
be found at <http://www.kame.net/> and <http://www.linux-ipv6.org/>. A list
of host and router implementations can be found at
* Besides the official RFC archive at <ftp://ftp.isi.edu/in-notes>, information
on IPv6 can be found at several web sites. First and foremost, the 6Bone's
web page at <http://www.6bone.net/> must be mentioned. 6Bone was started as
the testbed for IPv6, and is now an important part of the IPv6-connected
world. Other web pages that contain IPv6-related contents include
<http://www.ipv6.org/>, <http://playground.sun.com/pub/ipng/html/> and
<http://www.ipv6forum.com/>. Most of these sites carry further links - be
sure to have a look!
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