Border GW interface address configuration

[iores]

Hi,

why border GW needs to have a loopback interface configured with the same IP address as anycast gateway?

As far as I understand, this is because the border GW needs to advertise this network to the external L3 network and by configuring loopback with the same IP address as anycast gateway tricks border GW to advertise the routes to endpoint subnets without really knowing the routes to them.

How border router doesn't know the routes to endpoints subnets although they are part of the same fabric?

[jedolphi]

Hi iores, it is used to seed a Border Node BGP route for the IP range within the SD-Access Fabric Site, this route is often advertised in EBGP from Border Node to external routing devices such as a fusion device. On the Border Node you'll see both a network statement for the loopback interface (which configured with the same IP address as an Anycast Gateway) and an BGP aggregate-address representing the whole Anycast Gateway IP range. Cheers, Jerome