Red Hat Knowledgebase

Release Found: Red Hat Enterprise Linux

Symptom:
You see duplicate (DUP!) ping responses from ping output.

64 bytes from 10.1.22.15: icmp_seq=0 ttl=64 time=0.224 ms
64 bytes from 10.1.22.15: icmp_seq=1 ttl=64 time=0.234 ms
64 bytes from 10.1.22.15: icmp_seq=1 ttl=64 time=0.239 ms (DUP!)
64 bytes from 10.1.22.15: icmp_seq=1 ttl=64 time=0.247 ms (DUP!)
64 bytes from 10.1.22.15: icmp_seq=2 ttl=64 time=0.235 ms
64 bytes from 10.1.22.15: icmp_seq=2 ttl=64 time=0.242 ms (DUP!)
64 bytes from 10.1.22.15: icmp_seq=3 ttl=64 time=0.209 ms
64 bytes from 10.1.22.15: icmp_seq=3 ttl=64 time=0.249 ms (DUP!)
64 bytes from 10.1.22.15: icmp_seq=3 ttl=64 time=0.253 ms (DUP!)

Solution:
This could be caused by one of many things such as duplicate hosts on the network with the same IP address, faulty hardware, or a misconfigured network. To check if you have hosts sharing the same IP address, execute tcpdump while running the ping command.

For example:

tcpdump -i eth1 -te host <src ip address> and  host <target ip address>

This will give the MAC address of the target host and signify if there are two hosts responding to the ping.