MPLS load balancing

Unanswered Question
Oct 19th, 2009
User Badges:


I have 3 STM-1 equal cost links between two GSR12000 within my MPLS core. My problem is that load balancing/sharing of traffic passing via this links is done ONLY in one way and not both ways. OSPF is running as an IGP protocol.

Can you please advice of how to achieve balancing/sharing of traffic both ways.


  • 1
  • 2
  • 3
  • 4
  • 5
Overall Rating: 0 (0 ratings)
virverma Tue, 10/20/2009 - 00:55
User Badges:
  • Silver, 250 points or more

When multiple TE tunnels have the same cost, traffic can be load-balanced across them. Traffic

can also be load-balanced between the native IP path and TE tunnels if the cost of the routing is

the same. This situation has some restrictions, however; see the earlier section “Cost Calculation

of IGP Routes over TE Tunnels.” When you are load balancing over TE tunnels, the load balancing

can even be unequal cost load balancing. The load balancing of traffic is weighted proportionally

to the bandwidth requirement of the TE tunnels. If you have one tunnel with 80 MB and one with

20 MB of reserved bandwidth, the load-balancing ratio is 4:1, or the first tunnel should get four

times more traffic than the second tunnel. However, the load-balancing ratio is an approximation,

because Cisco Express Forwarding (CEF) has only 16 hash buckets. See Chapter 6, “Cisco

Express Forwarding,” for more on this.

When an LSR performs the load balancing over one or more IP paths and one or more TE tunnels,

it is always equal cost load balancing. This means that every path gets the same amount of traffic.

Multiple TE tunnels can be handy when the amount of bandwidth to be reserved between a pair

of routers is more than the bandwidth capacity of the links. You can then just create multiple TE

tunnels with each a piece of the required bandwidth.

huydien3384 Tue, 10/27/2009 - 23:50
User Badges:


Which algorithms do cisco routers use for load balancing?

Thank you


This Discussion