Tuesday, March 23, 2021

Unequal-Cost Multipath in Link State Protocols

TL&DR: You get unequal-cost multipath for free with distance-vector routing protocols. Implementing it in link state routing protocols is an order of magnitude more CPU-consuming.

Continuing our exploration of the Unequal-Cost Multipath world, why was it implemented in EIGRP decades ago, but not in OSPF or IS-IS?

Ignoring for the moment the “does it make sense” dilemma: finding downstream paths (paths strictly shorter than the current best path) is a side effect of running distance vector algorithms.

For a more formal discussion of loop-free alternates and downstream paths, please read RFC 5714 and RFC 5286.


source https://blog.ipspace.net/2021/03/ucmp-link-state-protocols.html?utm_source=atom_feed

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