"arp" or "ip neigh" showing hardware MAC address as INCOMPLETE

Solution Verified - Updated -

Issue

  • Losing network connectivity on gateway or router or firewall failover
  • arp output getting Hardware address as (incomplete)
# arp -n
IP address       HW type     Flags       HW address            Mask     Device
10.0.0.245                              (incomplete)                     eth0
10.0.0.254       ether        c         00:21:d7:aa:bb:cc                eth0
  • ip neighbour shows a MAC address as INCOMPLETE
# ip neigh
10.0.0.254 dev eth0 lladdr 00:21:d7:aa:bb:cc REACHABLE
10.0.0.245 dev eth0  INCOMPLETE

Environment

  • Red Hat Enterprise Linux
  • IPv4 network

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