EVPN multisite back-to-back model

[ab5]

Hi,

I have some questions about VXLAN EVPN Multi-Site using BGW back-to-back model.

Documentation says that the minimum back-to-back-topology is a square when having two BGWs per site. So apart from connection between sites, BGWs also have to be connected within site.

If i have understood correctly, this link is for forwarding BUM traffic between nondesignated and designated forwarder.

https://www.cisco.com/c/en/us/products/collateral/switches/nexus-9000-series-switches/white-paper-c11-739942.html

I can't find any configuration example that have back-to-back model and 2 BGWs per site.

Does anyone know if there is some special configuration needed for the connection between the BGW within site?

Or is it enough to configure it as a L3 link with for example iBGP between them? Then we should also be able to use it as an backup link to reach the BGWs at the remote site?

[Sergiu.Daniluk]

According to the whitepaper, "the Layer 3 underlay between all BGWs is achieved with a point-to-point subnet and the advertisement of the virtual IP and PIP addresses of the BGWs into this routing domain. " - this includes the connection between the BGWs in the same site . This can be confirmed in topology Figure 13, where BUM traffic coming from Site1 reaches BGW1, then is flooded directly to site 2 + flood to BGW2 from Site1.

In other words, the link that needs to be connected between the BGW from the same site is actually in the Site-external underlay.

For the site-internal underlay, it's sufficient that each BGW to be connected to all spines.

Stay safe,

Sergiu

[srinivas.talavagera]

Hi Dude,

Back to Back to BGW square model on dark fiber. Understand that point point L3 between Site1  BGWs and Site BGWs on back to back model. Do we need to run eBGP on these ports? please provide the config if possible.