Numbered BGP Config on SONiC

[fzakfeld]

I need to connect a router for upstream connectivity to the SONiC switches via BGP. Due to some limitations within the external architecture I won't have any direct connections available, but rather some L2 switching in between.

Due to this limitation, I need to have manual IP addresses assigned to the peering interface, as well as a numbered BGP session (remote-as can still be 'external' but the neighbor needs to be an IP address)

...
    "INTERFACE": {
        "Ethernet16": {},
        "Ethernet16|192.168.1.1/24": {},
        "Ethernet16|2001:db8::1/64": {}
    },
...
    "BGP_NEIGHBOR": {
        "default|192.168.1.2": {
            "asn": "65001"
        },
        "default|192.168.1.3": {
            "asn": "65001"
        }
    },
    "BGP_NEIGHBOR_AF": {
        "default|192.168.1.2|ipv4_unicast": {
            "admin_status": "true"
        },
        "default|192.168.1.3|ipv4_unicast": {
            "admin_status": "true"
        }
    },
...

Additionally it would be required to enable BFD, because of the lack of link state all the way through to the neighbor.

[fzakfeld]

The "IP address on interface" part should be pretty straightforward, like

- ip_address:
    address: 10.141.170.3/24
    assigned_object:
      name: Eth1/15/1
      device: leafsw01

on the corresponding switch.

The BGP neighbours be implemented using custom fields on the switches. I'd imagine something like:

- device:
    name: leafsw01
    custom_fields:
      sonic_bgp_neighbors:
        - neighbor: "10.141.170.1"
          vrf: foo
        - neighbor: "10.141.170.2"
          vrf: foo

(Could also be bound to the device_interface)

One important factor to consider is that one Interface does not mean one neighbour here, as there is L2 in between