I commonly see BGP configured on a provider (P/PE) router like this (this is a real router snippet just anonymised);
router bgp 12345
neighbour 1.1.1.1 remote-as 12345 ! iBGP peer
address-family ipv4
neighbour 1.1.1.1 remote-as 12345 ! iBGP peer
address-family vpnv4
neighbour 1.1.1.1 remote-as 12345 ! iBGP peer
address-family ipv4 vrf Customer1
neighbour 10.0.0.1 remote-as 67890 ! eBGP peer
- I understand the CE peering defined under "address-family ipv4 vrf Customer1" because we are placing their routes into that VRF
- I understand that "address-family vpnv4" is used to define provider iBGP peers to which other CE's are going to be attached, carrying this customer VRF
- Finally, I understand that a provider router is an iBGP peer so it is defined directly under "router bgp 12345"
What is the need for "address-family ipv4" (without vrf) here, or ever?
What does it provies that "normal" "neighbour" definitions (those directly under "router bgp 12345") and "vpnv4 neighbour" definitions, don't provide?
