Load Balancing in an MPLS Network > Traffic Flows Before Load Balancing

Purpose

The following sample output illustrates the details to look for when you issue different show commands to check if traffic is balanced. The following output is before load balancing is configured and is taken from transit router R2 in the network shown in Figure 10.

Action

To check the distribution of traffic across interfaces and LSPs, use the following CLI operational mode commands:

user@host> show route | find mpls 

user@host> monitor interface traffic

user@host> show mpls lsp statistics 

Sample Output 1

user@R2> show route | find mpls 

mpls.0: 8 destinations, 8 routes (8 active, 0 holddown, 0 hidden)

+ = Active Route, - = Last Active, * = Both

0                  *[MPLS/0] 1d 00:12:08, metric 1

                      Receive

1                  *[MPLS/0] 1d 00:12:08, metric 1

                      Receive

2                  *[MPLS/0] 1d 00:12:08, metric 1

                      Receive

100112             *[RSVP/7] 13:10:36, metric 1

                    > via so-0/0/1.0, label-switched-path lsp1

100128             *[RSVP/7] 13:01:08, metric 1

                    > via so-0/0/1.0, label-switched-path lsp4

100144             *[RSVP/7] 00:26:49, metric 1

                    > to 10.0.12.13 via fe-0/1/0.0, label-switched-path r0-r6

100160             *[RSVP/7] 00:23:25, metric 1

                    > via so-0/0/2.0, label-switched-path lsp2

100176             *[RSVP/7] 00:23:25, metric 1

                    > via so-0/0/2.0, label-switched-path lsp3

Sample Output 2

user@R2> monitor interface traffic

R2                                Seconds: 89                  Time: 14:33:09

Interface    Link  Input packets        (pps)     Output packets        (pps)

 so-0/0/0      Up              0          (0)                  0          (0)

 so-0/0/1      Up             90          (1)                 91          (1)

 so-0/0/2      Up            118          (1)             100122          (0)

 so-0/0/3      Up              0          (0)                  0          (0)

 fe-0/1/0      Up         100119          (0)                115          (0)

 fe-0/1/1      Up              0          (0)                  0          (0)

 fe-0/1/2      Up              0          (0)                  0          (0)

 fe-0/1/3      Up              0          (0)                  0          (0)

 [...Output truncated...]

Sample Output 3

user@R2> show mpls lsp statistics 

Ingress LSP: 0 sessions

Total 0 displayed, Up 0, Down 0

Egress LSP: 0 sessions

Total 0 displayed, Up 0, Down 0

Transit LSP: 5 sessions

To              From            State     Packets            Bytes LSPname

192.168.0.1     192.168.6.1     Up              0                0 lsp2

192.168.0.1     192.168.6.1     Up         112026         22853304 lsp1

192.168.0.1     192.168.6.1     Up              0                0 lsp3

192.168.0.1     192.168.6.1     Up              0                0 lsp4

192.168.6.1     192.168.0.1     Up              0                0 r0-r6

Total 5 displayed, Up 5, Down 0

What It Means

Sample Outputs 1 through 3 from transit router R2 show that traffic is not balanced across LSPs or interfaces.

Sample Output 1 for the show route command shows that all LSPs have the same metric (1) to the destination, even though they are traversing different interfaces. lsp1 and lsp4 are using so-0/0/1, while lsp2 and lsp3 are using so-0/0/2.

Sample Output 2 for the monitor interface traffic command shows that traffic is not evenly balanced across interfaces so-0/0/1 and so-0/0/2. Almost all traffic is going out so-0/0/2.

Sample Output 3 for the show mpls lsp statistics command shows that traffic across LSPs is not balanced. All traffic is going over lsp1.