Tuesday, January 6, 2009

IE Vol 1: MPLS TE Unequal Cost Load Balancing Complete

This time, we create two tunnels. One uses explicit paths, the other uses dynamic paths. Setting the traffic-eng bandwidth different on each tunnel causes unequal-cost load-balancing to occur.

One troubleshooting note, there are three requirements to have the TE tunnels show in the routing table:
  • tunnel mpls traffic-eng autoroute announce must be configured on each tunnel
  • the TE tunnels must show up/up in sh mpls traf tun brie
  • the TE tunnels must have ip unnumbered or an IP address assigned
Not having an IP unnumbered assigned to the tunnel interfaces caused me a lot of grief. Everything showed up and functioning, but I didn't see the tunnels in the routing table. Once I added ip unnumbered loo0, everything looked great. Note the traffic share counts that are different between the two paths. Try doing that in OSPF without MPLS-TE!

R4#sh ip route
Routing entry for
Known via "ospf 1", distance 110, metric 5, type intra area
Routing Descriptor Blocks:
* directly connected, via Tunnel0
Route metric is 5, traffic share count is 2
directly connected, via Tunnel1
Route metric is 5, traffic share count is 1

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