#Some quick info about MPLS:
You need to compile your kernel with options MPLS and psuedo-device ifmpls
For pure LSR - that only switch labels without encap/decap from other protocols (e.g. INET) - you need to work on routing table, ONLY. For example:
# route add -mpls 41 -tag 25 -inet 193.28.151.97
add host 41: gateway 193.28.151.97
# route add -mpls 42 -tag 30 -inet 193.28.151.97
add host 42: gateway 193.28.151.97
# route add -mpls 51 -tag 25 -inet 193.28.151.97
add host 51: gateway 193.28.151.97
Translation of first line: if it receives an MPLS frame with label 41 forward it to INET next-hop 193.28.151.97, but switch (change) label 41 with label 25
You also need to tweak sysctl to accept and forward MPLS:
# sysctl -w net.mpls.accept=1
net.mpls.accept: 0 -> 1
# sysctl -w net.mpls.forwarding=1
net.mpls.forwarding: 0 -> 1
Verify routes with route get or better with netstat -nrT:
...
MPLS:
Destination Gateway Flags Refs Use Mtu Tag Interface
41 193.28.151.97 UGHS 0 37241 - 25 sk0
42 193.28.151.97 UGHS 0 0 - 30 sk0
51 193.28.151.97 UGHS 0 0 - 25 sk0
#Interacting with other protocols
If you want to also decapsulate/encapsulate from MPLS to some other protocol (like INET or INET6), then you have to create an mpls interface and put in up state.
# ifconfig mpls0 create up
After that, create routes using ifa flag in order to specify the source interface (used for source IP Address of host generated packets), but route them through mpls0 interface.
# route add 204.152.190.0/24 -ifa 193.28.151.105 -ifp mpls0 -tag 25 -inet 193.28.151.97
add net 204.152.190.0: gateway 193.28.151.97
Verify the route:
# route -n get 204.152.190.0/24
route to: 204.152.190.0
destination: 204.152.190.0
mask: 255.255.255.0
gateway: 193.28.151.97
Tag: 25
local addr: 193.28.151.105
interface: mpls0
flags:
recvpipe sendpipe ssthresh rtt,msec rttvar hopcount mtu expire
0 0 0 813 344 0 0 0
sockaddrs:
or with netstat -rT:
...
204.152.190/24 193.28.151.97 UGS 0 95362 - 25 mpls0
...
Test if it's working using traceroute -M. Notice first hop is reporting label 25.
# traceroute -M 204.152.190.12
traceroute to 204.152.190.12 (204.152.190.12), 64 hops max, 40 byte packets
1 shaitan.girsa.ro (193.28.151.97) 2.892 ms 1.957 ms 1.992 ms [MPLS: Label 25 Exp 0]
2 b4-vlan811.girsa.ro (193.28.151.82) 1.988 ms 1.961 ms 1.989 ms [MPLS: Label 27 Exp 0]
3 80.97.219.81 (80.97.219.81) 1.990 ms 1.974 ms 2.009 ms
4 vlan103.cr3-sw.buch.artelecom.net (80.97.199.1) 2.651 ms 2.280 ms 3.663 ms
5 10.0.241.189 (10.0.241.189) 33.944 ms 34.011 ms 33.869 ms [MPLS: Label 21669 Exp 0]
6 10.0.240.22 (10.0.240.22) 33.946 ms 33.689 ms 33.929 ms
7 20gigabitethernet4-3.core1.fra1.he.net (80.81.192.172) 35.930 ms 35.926 ms 35.917 ms
8 10gigabitethernet1-2.core1.par1.he.net (72.52.92.89) 43.940 ms 45.900 ms 47.916 ms
9 10gigabitethernet1-3.core1.lon1.he.net (72.52.92.33) 59.901 ms 51.888 ms 51.913 ms
10 10gigabitethernet4-4.core1.nyc4.he.net (72.52.92.241) 119.808 ms 119.780 ms 119.800 ms
11 10gigabitethernet1-2.core1.chi1.he.net (72.52.92.102) 141.755 ms 143.748 ms 149.756 ms
12 he.ord1.isc.org (209.51.161.18) 143.756 ms 143.757 ms 141.755 ms
13 iana.r1.ord1.isc.org (199.6.0.1) 145.831 ms 141.747 ms 143.762 ms
14 int-0-0-1-8.r1.pao1.isc.org (149.20.65.157) 201.653 ms 205.650 ms 201.650 ms [MPLS: Label 16005 Exp 0]
15 int-0-0-1-0.r2.sql1.isc.org (149.20.65.10) 201.663 ms 201.645 ms 201.664 ms
16 www.netbsd.org (204.152.190.12) 199.676 ms 201.652 ms 201.673 ms
See also [[LDP]] wiki page.