EVPN Fabric with eBGP to WAN

Hallo @ all,

i have a question regarding EVPN fabric and the connection to the WAN and i want to create the following topology.

There are N5k's as leaf-switches and N77k as spine-switch. There are also ASR9k, which are configured as L3out, so there is a VXLAN overlay between the leafs and the ASR9k. I have the following config on the ASR9k:

vrf SERV
address-family ipv4 unicast
import route-target
65000:10000 stitching
!
export route-target
65000:10000
65000:10000 stitching
!
!
!
interface BVI1500
vrf SERV
ipv4 address xxx.xxx.xxx
!
interface nve1
member vni 10000
vrf SERV
host-reachability protocol bgp
!
overlay-encapsulation vxlan
source-interface Loopback1
!
router bgp 65000
bgp router-id x.x.x.x
address-family ipv4 unicast
!
address-family vpnv4 unicast
!
address-family l2vpn evpn
retain route-target all
!
neighbor x.x.x.y
remote-as 65000
password encrypted xxxxxxxx
update-source Loopback0
address-family l2vpn evpn
import stitching-rt re-originate
encapsulation-type vxlan
advertise vpnv4 unicast re-originated
default-originate
soft-reconfiguration inbound
advertise l2vpn evpn disable

As you see from the configuration, the BGP-Session between the ASR9k and Nexus77k is iBGP. My question is now, if eBGP would also be possible in that kind of setup and what are the differences of using iBGP vs eBGP?

Point is that the ASR9k is part of the WAN and i wanna have different AS numbers between WAN and DC. In the end, the EVPN routes should be stitched as VPNv4 routes into the WAN and vice versa.

best regards
Mario

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