Technical Documentation - Static VXLAN Tunnels


I was reading the following documentation (https://docs.cumulusnetworks.com/display/DOCS/Static+VXLAN+Tunnels#) and noticed that there are different BGP AS #'s being used for the spine's (backplane). Is this a mistake?

ECMP only works to the same AS # with the same metric's.

2 replies

1) BGP multi-path across diverse AS_PATH
in BGP there is a knob to modify the BGP bestpath algorithm and ignore the AS_PATH source (AS 100 versus AS 200) then you can use BGP multi-path across multiple AS numbers (assuming AS_PATH is equal length).

NCLU command is " net add bgp bestpath as-path multipath-relax "

It's true there's several path attributes that must be equal for the route path to be a candidate for multi-path

2) BGP multi-path using unequal cost
BGP supports multi-path, whether the paths have equal costs or unequal costs, though not all implementations support unequal-cost multi-path. It's on the roadmap for FRR routing suite (feel free to contact us through official channels if this is an urgent requirement).

https://docs.cumulusnetworks.com/display/DOCS/Border+Gateway+Protocol+-+BGP

Additionally you might find this ebook a helpful resource for BGP in the Data Center environment:
https://cumulusnetworks.com/blog/ultimate-bgp-guide/
Thanks!

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