I know that OSPF will load balance across equal cost paths such as:

R1 ------------------ R3
|     100mbit          |
|                      |
|                 1gbit|
|100mbit               |
|                      |
|        1gbit         |
R2------------------- R4

A stream going between R1 and R4 will be broken up such that packet 1 goes to R2, packet 2 R3, packet 3 R2, etc.

Now lets say the link from R1 to R3 was upgraded to 1gbit. I know that I could manipulate the link costs to achieve equal cost load balancing across both links. However these links (R1->R3 : R1->R2) are in a 10:1 ratio of each other to fully utilize each link. Is it possible to load balance in a 10:1 ratio?

I'm not sure if this is native to OSPF. If not is there another Cisco (or otherwise) mechanism to achieve this.


You could use EIGRP to achieve load balancing across unequal cost links (variance setting)

  • Correct, Cisco's OSPF implementation doesn't support unequal cost LB – Mike Pennington Nov 20 '13 at 11:53

I think you can force the ospf cost using 'ip ospf cost X' statement to set the same on both interfaces on R1. Your router will then load balance the traffic over the two interfaces.

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