MPLS TE Static Routes

Once your MPLS Traffic Engineering (TE) tunnel is up and running, it won’t be used automatically. It acts like any other physical interface or (GRE) tunnel. You have to route traffic down your tunnel. One of the options we can use is to use a static route. In the MPLS TE IS-IS configuration lesson, we configured an MPLS TE topology with a tunnel interface. In this lesson, we’ll route some traffic down the tunnel using a static route.

Configuration

Let’s see how we configure a static route. This is the topology I’ll use:

Mpls Te Pe C Router Topology Tunnel

Routers PE1, P1, P2, P3, and PE2 run MPLS TE. We have a TE tunnel from PE1 to PE2. All routers run IOSv 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.

Let’s take a look at our tunnel:

PE1#show mpls traffic-eng tunnels Tunnel 1

Name: PE1_t1                              (Tunnel1) Destination: 6.6.6.6
  Status:
    Admin: up         Oper: up     Path: valid       Signalling: connected
    path option 1, type dynamic (Basis for Setup, path weight 20)

  Config Parameters:
    Bandwidth: 750      kbps (Global)  Priority: 7  7   Affinity: 0x0/0xFFFF
    Metric Type: TE (default)
    AutoRoute:  disabled  LockDown: disabled  Loadshare: 750      bw-based
    auto-bw: disabled
  Active Path Option Parameters:
    State: dynamic path option 1 is active
    BandwidthOverride: disabled  LockDown: disabled  Verbatim: disabled


  InLabel  :  - 
  OutLabel : GigabitEthernet0/1, 26
  RSVP Signalling Info:
       Src 2.2.2.2, Dst 6.6.6.6, Tun_Id 1, Tun_Instance 18
    RSVP Path Info:
      My Address: 192.168.23.2   
      Explicit Route: 192.168.23.3 192.168.36.3 192.168.36.6 6.6.6.6 
      Record   Route:   NONE
      Tspec: ave rate=750 kbits, burst=1000 bytes, peak rate=750 kbits
    RSVP Resv Info:
      Record   Route:   NONE
      Fspec: ave rate=750 kbits, burst=1000 bytes, peak rate=750 kbits
  Shortest Unconstrained Path Info:
    Path Weight: 20 (TE)
    Explicit Route: 192.168.23.2 192.168.23.3 192.168.36.3 192.168.36.6 
                    6.6.6.6 
  History:
    Tunnel:
      Time since created: 4 minutes
      Time since path change: 3 minutes, 7 seconds
      Number of LSP IDs (Tun_Instances) used: 18
    Current LSP:
      Uptime: 3 minutes, 7 seconds

The tunnel is up and running and shows up as connected. The tunnel goes through P1. Let’s check our routing table:

PE1#show ip route
Codes: L - local, C - connected, S - static, R - RIP, M - mobile, B - BGP
       D - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter area 
       N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2
       E1 - OSPF external type 1, E2 - OSPF external type 2
       i - IS-IS, su - IS-IS summary, L1 - IS-IS level-1, L2 - IS-IS level-2
       ia - IS-IS inter area, * - candidate default, U - per-user static route
       o - ODR, P - periodic downloaded static route, H - NHRP, l - LISP
       a - application route
       + - replicated route, % - next hop override, p - overrides from PfR

Gateway of last resort is not set

      1.0.0.0/32 is subnetted, 1 subnets
i L2     1.1.1.1 [115/20] via 192.168.12.1, 00:06:10, GigabitEthernet0/0
      2.0.0.0/32 is subnetted, 1 subnets
C        2.2.2.2 is directly connected, Loopback0
      3.0.0.0/32 is subnetted, 1 subnets
i L2     3.3.3.3 [115/20] via 192.168.23.3, 00:05:46, GigabitEthernet0/1
      4.0.0.0/32 is subnetted, 1 subnets
i L2     4.4.4.4 [115/20] via 192.168.24.4, 00:06:10, GigabitEthernet0/2
      5.0.0.0/32 is subnetted, 1 subnets
i L2     5.5.5.5 [115/30] via 192.168.24.4, 00:06:00, GigabitEthernet0/2
      6.0.0.0/32 is subnetted, 1 subnets
i L2     6.6.6.6 [115/30] via 192.168.23.3, 00:05:19, GigabitEthernet0/1
      7.0.0.0/32 is subnetted, 1 subnets
i L2     7.7.7.7 [115/40] via 192.168.23.3, 00:05:19, GigabitEthernet0/1
      192.168.12.0/24 is variably subnetted, 2 subnets, 2 masks
C        192.168.12.0/24 is directly connected, GigabitEthernet0/0
L        192.168.12.2/32 is directly connected, GigabitEthernet0/0
      192.168.23.0/24 is variably subnetted, 2 subnets, 2 masks
C        192.168.23.0/24 is directly connected, GigabitEthernet0/1
L        192.168.23.2/32 is directly connected, GigabitEthernet0/1
      192.168.24.0/24 is variably subnetted, 2 subnets, 2 masks
C        192.168.24.0/24 is directly connected, GigabitEthernet0/2
L        192.168.24.2/32 is directly connected, GigabitEthernet0/2
i L2  192.168.36.0/24 [115/20] via 192.168.23.3, 00:05:46, GigabitEthernet0/1
i L2  192.168.45.0/24 [115/20] via 192.168.24.4, 00:06:10, GigabitEthernet0/2
i L2  192.168.56.0/24 [115/30] via 192.168.24.4, 00:05:19, GigabitEthernet0/2
                      [115/30] via 192.168.23.3, 00:05:19, GigabitEthernet0/1
i L2  192.168.67.0/24 [115/30] via 192.168.23.3, 00:05:19, GigabitEthernet0/1

At the moment, we don’t use this tunnel at all. Let’s say I want to reach the loopback interface of CE2. We can create a static route like this:

PE1(config)#ip route 7.7.7.7 255.255.255.255 Tunnel 1

That’s all there is to it.

Verification

Let’s verify our work. First, we’ll look at the routing table:

PE1#show ip route 7.7.7.7
Routing entry for 7.7.7.7/32
  Known via "static", distance 1, metric 0 (connected)
  Routing Descriptor Blocks:
  * directly connected, via Tunnel1
      Route metric is 0, traffic share count is 1

This looks good. Traffic destined for 7.7.7.7 goes through the tunnel. If you want to see all destinations that use the tunnel, then you can use the show mpls forwarding-table command:

PE1#show mpls forwarding-table
Local      Outgoing   Prefix           Bytes Label   Outgoing   Next Hop    
Label      Label      or Tunnel Id     Switched      interface              
16         No Label   1.1.1.1/32       0             Gi0/0      192.168.12.1
17         Pop Label  4.4.4.4/32       0             Gi0/2      192.168.24.4
18         Pop Label  192.168.45.0/24  0             Gi0/2      192.168.24.4
19         22         5.5.5.5/32       0             Gi0/2      192.168.24.4
20         25         192.168.56.0/24  0             Gi0/1      192.168.23.3
           23         192.168.56.0/24  0             Gi0/2      192.168.24.4
21         Pop Label  3.3.3.3/32       0             Gi0/1      192.168.23.3
22         Pop Label  192.168.36.0/24  0             Gi0/1      192.168.23.3
23         27         6.6.6.6/32       0             Gi0/1      192.168.23.3
24    [T]  Pop Label  7.7.7.7/32       0             Tu1        point2point 
25         29         192.168.67.0/24  0             Gi0/1      192.168.23.3

[T]     Forwarding through a LSP tunnel.
        View additional labelling info with the 'detail' option

The [T] tells us that we reach 7.7.7.7 through the tunnel.  If you want to see some detail, add the detail parameter:

PE1#show mpls forwarding-table 7.7.7.7 detail 
Local      Outgoing   Prefix           Bytes Label   Outgoing   Next Hop    
Label      Label      or Tunnel Id     Switched      interface              
24         Pop Label  7.7.7.7/32       0             Tu1        point2point 
        MAC/Encaps=14/18, MRU=1500, Label Stack{26}, via Gi0/1
        5254001A70435254001F16328847 0001A000
        No output feature configured

The output above tells us we use the tunnel interface. You can also look at the CEF table directly:

PE1#show ip cef 7.7.7.7 detail
7.7.7.7/32, epoch 0, flags [attached]
  dflt local label info: global/24 [0x1]
  attached to Tunnel1

Let’s try a trace:

PE1#traceroute 7.7.7.7 source Loopback 0 numeric probe 1
Type escape sequence to abort.
Tracing the route to 7.7.7.7
VRF info: (vrf in name/id, vrf out name/id)
  1 192.168.23.3 [MPLS: Label 26 Exp 0] 4 msec
  2 192.168.36.6 4 msec
  3 192.168.67.7 6 msec

Or send some pings:

PE1#ping 7.7.7.7 repeat 100
Type escape sequence to abort.
Sending 100, 100-byte ICMP Echos to 7.7.7.7, timeout is 2 seconds:
!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

If you look at the tunnel, you can see the number of sent packets:

PE1#show interfaces Tunnel 1 | include output           
  Last input never, output 00:00:02, output hang never
  Input queue: 0/75/0/0 (size/max/drops/flushes); Total output drops: 0
  5 minute output rate 1000 bits/sec, 1 packets/sec
     130 packets output, 11341 bytes, 0 underruns
     0 output errors, 0 collisions, 0 interface resets
     0 output buffer failures, 0 output buffers swapped out

That’s all there is to it. Once your tunnel is up and running, a static route works the same as for any other interface.

  • 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 that you can use a static route to send traffic down an MPLS TE tunnel. This can be a simple solution if you want to send specific traffic to a specific destination down the TE tunnel. If you have any questions, please leave a comment.