Hi, Is there a way to have a cisco router fill up 1 link and then "overflow" to a second parallel link? The reason I don't want equal cost or round-robin is this situation:
I have a high reliability link A with bandwidth B_a and a lower reliability link B with bandwidth B_b. B_b > B_a. However, I want as much of the A link used as possible because it is the high reliability link. Extra usage should "spill-over" into link B.
Is this possible?
Thanks.
The Cisco 10000 series offers a dynamic bandwidth ratio feature that appears to perform a similar function, but I doubt that's the platform you're running. :-)
If you're running MPLS, I believe MPLS Traffic Engineering features might be utilized to accomplish your goal.
snipped-for-privacy@gmail.com wrote:
L2 load balancing can work this way (i.e. etherchannel), but generally load balancing at layer 3 is round robin on packet or flow, neither of which would fill up a pipe and then spill over into another. Perhaps you could do policy based routing and put your heavy hitters on one of the links and split it that way.
The routing protocols and the L3 forwarding do not normally take line utilisation into account so that won't work. The best route(s) is(are) in the routing table and line utilisation is not a factor because it could cause instability. Policy based routing doesn't know about it either.
I suggest you have a look at an output policy for your favoured link. It should be possible to prioritise traffic, ratelimit it to line speed and send remaining traffic to the next hop at the other end of the 2nd line. Depending on speed and hardware used you may run into practical limitations like max throughput and getting (close to) 100% load on the reliable line. You''ll have to do this in both directions.
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