Ping shows DUP! messages

Issue

• When pinging another machine, these messages show up:

64 bytes from 10.8.64.93: icmp_seq=43 ttl=61 time=1.64 ms
64 bytes from 10.8.64.93: icmp_seq=43 ttl=61 time=1.66 ms (DUP!)
64 bytes from 10.8.64.93: icmp_seq=44 ttl=61 time=0.921 ms
64 bytes from 10.8.64.93: icmp_seq=44 ttl=61 time=0.946 ms (DUP!)
64 bytes from 10.8.64.93: icmp_seq=45 ttl=61 time=0.686 ms
64 bytes from 10.8.64.93: icmp_seq=45 ttl=61 time=0.708 ms (DUP!)
64 bytes from 10.8.64.93: icmp_seq=46 ttl=61 time=0.853 ms
64 bytes from 10.8.64.93: icmp_seq=46 ttl=61 time=0.876 ms (DUP!)

• Also, when restarting network:

# service network restart
[...]
Activating interface eth3:  "dev" (eth3) must match "label" (eth0).
RTNETLINK answers: File exists
RTNETLINK answers: File exists
[...]