Symptom
Missing ARP entry causing BGP peering stuck in IDLE
TOPO as below:
N3K--1 SVI3011(192.168.2.1) --peerlink-- (192.168.2.2) SVI3011 N3K-02
N3K-1# show ip bgp summary vrf aaa
Neighbor V AS MsgRcvd MsgSent TblVer InQ OutQ Up/Down State/PfxRcd
192.168.2.2 4 65103 0 0 0 0 0 22:23:04 Idle <<<<<<<<<<<<<<<
N3K-1# ethanalyzer local interface inband display-filter ip.addr==192.168.2.1 limit-captured-frames 0
Capturing on inband
2020-06-18 14:10:43.052808 192.168.2.1 -> 224.0.0.13 PIMv2 Hello
2020-06-18 14:10:54.699631 192.168.2.2 -> 192.168.2.1 TCP 44889 > bgp [SYN] Seq=0 Win=29200 Len=0 MSS=1460 TSV=26674108 TSER=0 WS=2
2020-06-18 14:10:55.702438 192.168.2.2 -> 192.168.2.1 TCP 44889 > bgp [SYN] Seq=0 Win=29200 Len=0 MSS=1460 TSV=26674409 TSER=0 WS=2
2020-06-18 14:10:57.705771 192.168.2.2 -> 192.168.2.1 TCP 44889 > bgp [SYN] Seq=0 Win=29200 Len=0 MSS=1460 TSV=26675010 TSER=0 WS=2
2020-06-18 14:11:01.712411 192.168.2.2 -> 192.168.2.1 TCP 44889 > bgp [SYN] Seq=0 Win=29200 Len=0 MSS=1460 TSV=26676212 TSER=0 WS=2
bash-4.3$ ip netns exec aaa arp -a
? (192.168.2.2) at on Vlan3011 <<<<<<
Workaround
reload the effected device
