Dedicated MLAG peer group for overlay tenants

[ksantos01]

Enhancement summary

Currently MLAG-IPv4-UNDERLAY-PEER is used for the iBGP session between MLAG pairs in the underlay and overlay. This approach can be misleading due to the use of UNDERLAY word in the BGP peer group name.

The following is an example of the configuration that AVD generates today

router bgp xxxx 
   neighbor MLAG-IPv4-UNDERLAY-PEER peer group
   neighbor MLAG-IPv4-UNDERLAY-PEER remote-as 65000.1
   neighbor MLAG-IPv4-UNDERLAY-PEER next-hop-self
   neighbor MLAG-IPv4-UNDERLAY-PEER description DC1-CL2
   neighbor MLAG-IPv4-UNDERLAY-PEER password 7 xxxx
   neighbor MLAG-IPv4-UNDERLAY-PEER send-community
   neighbor MLAG-IPv4-UNDERLAY-PEER maximum-routes 12000
   neighbor MLAG-IPv4-UNDERLAY-PEER route-map RM-MLAG-PEER-IN in

   address-family ipv4
      neighbor MLAG-IPv4-UNDERLAY-PEER activate

   vrf BLUE
      rd 192.168.100.1:1002
      route-target import evpn 1002:1002
      route-target export evpn 1002:1002
      router-id 192.168.100.1
      neighbor 172.16.1.1 peer group MLAG-IPv4-UNDERLAY-PEER
      redistribute connected

Which component of AVD is impacted

eos_designs

Use case example

please detail your use case

Describe the solution you would like

A dedicated BGP peer group should be used for the iBGP session between MLAG pair in the overlay.

router bgp xxxx 
   neighbor MLAG-IPv4-OVERLAY-PEER peer group
   neighbor MLAG-IPv4-OVERLAY-PEER remote-as 65000.1
   neighbor MLAG-IPv4-OVERLAY-PEER next-hop-self
   neighbor MLAG-IPv4-OVERLAY-PEER description DC1-CL2
   neighbor MLAG-IPv4-OVERLAY-PEER password 7 xxxx
   neighbor MLAG-IPv4-OVERLAY-PEER send-community
   neighbor MLAG-IPv4-OVERLAY-PEER maximum-routes 12000
   neighbor MLAG-IPv4-OVERLAY-PEER route-map RM-MLAG-PEER-IN in

   address-family ipv4
      neighbor MLAG-IPv4-OVERLAY-PEER activate

   vrf BLUE
      rd 192.168.100.1:1002
      route-target import evpn 1002:1002
      route-target export evpn 1002:1002
      router-id 192.168.100.1
      neighbor 172.16.1.1 peer group MLAG-IPv4-OVERLAY-PEER
      redistribute connected

Describe alternatives you have considered

No response

Additional context

No response

Contributing Guide

• I agree to follow this project's Code of Conduct

[gmuloc]

Plan for this issue to be non-breaking:
1/ introduce a new knob to use_separate_mlag_peer_group_for_overlay: <bool> with a default of false.
2/ add a peer_group in bgp_peer_groups for MLAG overlay to be used when the toggle from 1/ is true