Tuesday, November 24, 2020

BGP as-prepending with single neighbour

2xVPNs via Internet to Azure from an on-prem device that has 2 separate ISP. The way Azure works, you have a single IP to use as BGP peer, for both connections, not 2 separate peer addresses. This is not configurable in Azure.

Because of this I cannot use as-prepend because I don't have 2 neighbors where to push two different route-maps (one normal and the other with the prepend AS).

Every now and then Azure decides to change and point to the secondary ISP, but the on-prem still has the primary ISP selected to reach Azure, which results in one way traffic. Only way for me to fix is to drop the secondary VPN through secondary ISP to get Azure to restore the primary path as preferred. Ideas on how to fix ? (I cannot have multiple gateways in Azure).



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