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

Solution Verified - Updated -


  • 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                              (incomplete)                     eth0       ether        c         00:21:d7:aa:bb:cc                eth0
  • ip neighbour shows a MAC address as INCOMPLETE
# ip neigh dev eth0 lladdr 00:21:d7:aa:bb:cc REACHABLE dev eth0  INCOMPLETE
  • Cannot see ARP Reply getting generated in the system after receiving the ARP Request from the source host.


  • Red Hat Enterprise Linux
  • IPv4 network

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