Hi all!
English is not my first language, so I am sorry in advance if my words confused you. I tried my best.
As far as I know, CEs don't have vrf in general, so CEs would use ipv4&ipv6 address family of BGP to form BGP neighbor with PEs and advertise CEs' ipv4 routes to PEs, and PEs use ipv4 vrf XXX & ipv6 vrf XXX address family of BGP to form BGP neighbor relationship with CEs and store the ipv4 routes from CEs in the ipv4 vrf XXX & ipv6 vrf XXX address family. Let's assume R1 is CE, R2 is PE, and R2 uses the ipv4 vrf customer1 address-family to form BGP neighbor with R1; The ipv4 routes that R2 received from R1 would be stored in the R2's ipv4 vrf customer1 address-family of the BGP, right?
But when I run show ip bgp all on PE, all the routes that received form CE are under the BGP vpnv4 section not in a section called ipv4 vrf customer1 unicast, why is that? Does Cisco assume that all the routes in the vrf of PE will advertise to other PEs, so the vpnv4 copies the ipv4 routes in all vrfs into the vpnv4 address-family and uses the name of the vrf (vrf customer1) to distinguish which ipv4 vrf the routes belong to? I also tried the show bgp vpnv4 unicast vrf customer1 neighbors 1.1.1.1 received-routes, why it's vpnv4 unicast not something like ip bgp vrf customoer1?
R2#show ip bgp all
For address family: IPv4 Unicast
For address family: IPv6 Unicast
For address family: VPNv4 Unicast
BGP table version is 248, local router ID is 2.2.2.2
Status codes: s suppressed, d damped, h history, * valid, > best, i - internal,
r RIB-failure, S Stale, m multipath, b backup-path, f RT-Filter,
x best-external, a additional-path, c RIB-compressed,
Origin codes: i - IGP, e - EGP, ? - incomplete
RPKI validation codes: V valid, I invalid, N Not found
Network Next Hop Metric LocPrf Weight Path
Route Distinguisher: 10000:1 (default for vrf customer1)
Network Next Hop Metric LocPrf Weight Path
*> 10.1.0.0/16 1.1.1.1 21 0 10001 ?
Route Distinguisher: 10000:2
*>i 10.4.0.0/16 4.4.4.4 21 0 40001 ?
Thanks!