MPLS TE Policy Based Routing (PBR)

As we have seen in the MPLS TE configuration lesson, no traffic is forwarded down an MPLS Traffic Engineering (TE) tunnel by default. It’s similar to a GRE tunnel. The tunnel is there but doesn’t do anything. You have to configure routing to forward traffic down the tunnel.

We have multiple options to route traffic down a TE tunnel. One of the options is Policy Based Routing (PBR). There is nothing special about this configuration. It’s straightforward PBR. We match specific traffic with a route map and set the TE tunnel interface as the next hop.

Configuration

This is the topology we’ll use:

Mpls Te Pe C Router Topology Tunnel

Routers PE1, P1, P2, P3, and PE2 run MPLS TE. We have a tunnel from PE1 to PE2. I use Cisco IOS Software, IOSv Software (VIOS-ADVENTERPRISEK9-M), Version 15.9(3)M4.

  • Configurations
  • CE1
  • CE2
  • P1
  • P2
  • P3
  • PE1
  • PE2

Want to take a look for yourself? Here you will find the startup configuration of each device.

Here is the routing table of PE1:

PE1#show ip route isis

      1.0.0.0/32 is subnetted, 1 subnets
i L2     1.1.1.1 [115/20] via 192.168.12.1, 00:04:02, GigabitEthernet0/0
      3.0.0.0/32 is subnetted, 1 subnets
i L2     3.3.3.3 [115/20] via 192.168.23.3, 00:03:52, GigabitEthernet0/1
      4.0.0.0/32 is subnetted, 1 subnets
i L2     4.4.4.4 [115/20] via 192.168.24.4, 00:04:12, GigabitEthernet0/2
      5.0.0.0/32 is subnetted, 1 subnets
i L2     5.5.5.5 [115/30] via 192.168.24.4, 00:03:52, GigabitEthernet0/2
      6.0.0.0/32 is subnetted, 1 subnets
i L2     6.6.6.6 [115/30] via 192.168.23.3, 00:03:14, GigabitEthernet0/1
      7.0.0.0/32 is subnetted, 1 subnets
i L2     7.7.7.7 [115/40] via 192.168.23.3, 00:03:14, GigabitEthernet0/1
i L2  192.168.36.0/24 [115/20] via 192.168.23.3, 00:03:52, GigabitEthernet0/1
i L2  192.168.45.0/24 [115/20] via 192.168.24.4, 00:04:12, GigabitEthernet0/2
i L2  192.168.56.0/24 [115/30] via 192.168.24.4, 00:03:14, GigabitEthernet0/2
                      [115/30] via 192.168.23.3, 00:03:14, GigabitEthernet0/1
i L2  192.168.67.0/24 [115/30] via 192.168.23.3, 00:03:14, GigabitEthernet0/1

As you can see above, we don’t use the tunnel interface. We’ll configure PBR to forward some traffic down our TE tunnel.

Let’s start with an access-list that matches traffic between the loopback interfaces of CE1 and CE2:

PE1(config)#ip access-list extended CE1_L0_CE2_L0
PE1(config-ext-nacl)#permit ip host 1.1.1.1 host 7.7.7.7

And we’ll create a route-map that matches the access-list and sets the tunnel as the next hop:

PE1(config)#route-map CE1_CE2_TUNNEL1 permit 10
PE1(config-route-map)#match ip address CE1_L0_CE2_L0
PE1(config-route-map)#set interface Tunnel 1

We’ll attach the route-map on the interface that connects to CE1:

PE1(config)#interface GigabitEthernet 0/0
PE1(config-if)#ip policy route-map CE1_CE2_TUNNEL1

This completes our configuration.

Verification

Let’s verify our work. I’ll enable a debug so we can see it in action:

PE1#debug ip policy
Policy routing debugging is on

Let’s send a ping from CE1 to CE2:

CE1#ping 7.7.7.7 source 1.1.1.1 repeat 1
Type escape sequence to abort.
Sending 1, 100-byte ICMP Echos to 7.7.7.7, timeout is 2 seconds:
Packet sent with a source address of 1.1.1.1 
!
Success rate is 100 percent (1/1), round-trip min/avg/max = 8/8/8 ms

This is what we see on our console:

PE1#
IP: s=1.1.1.1 (GigabitEthernet0/0), d=7.7.7.7, len 100, FIB policy match
IP: s=1.1.1.1 (GigabitEthernet0/0), d=7.7.7.7, len 100, PBR Counted
IP: s=1.1.1.1 (GigabitEthernet0/0), d=7.7.7.7 (Tunnel1), len 100, FIB policy routed

This is looking good. Traffic is forwarded down the tunnel. We can also verify this by looking at our route-map:

PE1#show route-map
route-map CE1_CE2_TUNNEL1, permit, sequence 10
  Match clauses:
    ip address (access-lists): CE1_L0_CE2_L0 
  Set clauses:
    interface Tunnel1
Interface tracking current: NULL
Tunnel1, adj_lh:0,oce:0,status:0

  Policy routing matches: 1 packets, 114 bytes

That’s all there is to it.

  • Configurations
  • CE1
  • CE2
  • P1
  • P2
  • P3
  • PE1
  • PE2

Want to take a look for yourself? Here you will find the final configuration of each device.

Conclusion

You have learned to use PBR to forward traffic down an MPLS TE tunnel. I hope you enjoyed this lesson. If you have any questions, please leave a comment.