CCIE Blog

Will a Cisco Router Load Balance Between an IP and MPLS Path?

R1 has two paths to the loopback on R4:

R1#sho ip route 10.1.1.4

Routing entry for 10.1.1.4/32

Known via “ospf 1″, distance 110, metric 129, type intra area

Last update from 192.168.12.2 on Serial1/0, 00:04:46 ago

Routing Descriptor Blocks:

192.168.13.3, from 10.1.1.4, 00:04:46 ago, via Serial1/1

Route metric is 129, traffic share count is 1

* 192.168.12.2, from 10.1.1.4, 00:04:46 ago, via Serial1/0

Route metric is 129, traffic share count is 1

However, R1 only has one labeled path through LSR R3.

R1#sho mpls forwarding-table 10.1.1.4

Local  Outgoing    Prefix            Bytes tag  Outgoing   Next Hop

tag    tag or VC   or Tunnel Id      switched   interface

20     20          10.1.1.4/32       0          Se1/1      point2point

R1#

Which path will R1 choose?

R1#trace 10.1.1.4

Type escape sequence to abort.

Tracing the route to 10.1.1.4

1 192.168.13.3 [MPLS: Label 20 Exp 0] 48 msec

192.168.12.2 44 msec

192.168.13.3 [MPLS: Label 20 Exp 0] 16 msec

2 192.168.24.4 48 msec

192.168.34.4 12 msec *

R1#

Contrary to what I have read (or maybe just misunderstood), it looks like the router WILL load balance between an IP path and an LSP!

Regards, Bryan (Blog by Bryan Bartik)