Question

IP load sharing on MLXE

  • 3 July 2019
  • 2 replies
  • 300 views

So here's the setup. We have an MLXe with 2 LAGs to a Cisco CMTS (cbr). these two are OSPF neighbors. The CMTS announces it's routes via iBGP to a Route Reflector elsewhere in the network.

what we're seeing is that traffic towards the CMTS is taking 1 LAG. Traffic out from the CMTS is load balanced fine it's just the traffic towards the CMTS that is lopsided. Is there a way on the MLXe to check the load sharing algorithm? Any ideas why it might pick one lag over the other with each being exactly the same OSPF cost?

Thanks

2 replies

I believe this is the same question you asked in the ticket you opened with us that I helped with.

For the community it was due to Multipath not being enabled for BGP. BGP (I or E) will only ever use 1 path by default. By configuring Multipath for BGP this allowed for the load sharing to take place between two equal cost paths.
config snippet I was missing:

router bgp
address-family ipv4 unicast
maximum-paths 8

Thanks Samantha!

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