Technical Documentation - Static VXLAN Tunnels

  • 13 October 2017
  • 2 replies

I was reading the following documentation ( 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

Userlevel 1
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).

Additionally you might find this ebook a helpful resource for BGP in the Data Center environment: