Symptom
On BGW, the overlay default route is pointing correctly to the shared border NVE (loopback 1):
N9k-test# sh ip route 0.0.0.0 vrf VRF
IP Route Table for VRF ?VRF?
'*' denotes best ucast next-hop
'**' denotes best mcast next-hop
'[x/y]' denotes [preference/metric]
'%' in via output denotes VRF
0.0.0.0/0, ubest/mbest: 1/0
*via 10.10.1.5%default, [20/0], 01:06:09, bgp-1.1, external, tag 65530 (evpn) segid: 50000 tunnelid: 0xada0104 encap: VXLAN
The underlay next-hop 10.10.1.5 (shared border) is reachable over Eth1/5:
N9k-test# sh ip route 10.10.1.5
IP Route Table for VRF "default"
'*' denotes best ucast next-hop
'**' denotes best mcast next-hop
'[x/y]' denotes [preference/metric]
'%' in via output denotes VRF
10.218.1.4/32, ubest/mbest: 1/0
*via 10.10.0.4, Eth1/5, [110/4], 01:07:18, ospf-UNDERLAY, intra
The problem is that no ARP request is triggered on Eth1/5 by the switch connected to the shared border even if it is receiving VXLAN traffic from the client that needs to be forwarded. As a result, that VXLAN traffic towards the shared-border is sent to destination mac 0000.0000.0000 over Eth1/5, and then dropped on the shared border.
Conditions
No ARP entry exists for underlay nexthop.
Workaround
Issue a ping on the BGW to the underlay next hop to trigger an ARP request.
(Static ARP does not work as a workaround.)
