Day: June 2, 2015

When ping fails try arping

Sometimes when ping insist to fail you can try arping to know if the machine is online.

First verify with arp command if it has some idea about the physical address:

$ arp -n
Address                  HWtype  HWaddress           Flags Mask            Iface
192.168.0.16             ether   7c:dd:90:1e:83:71   C                     wlan0

Good, it knows about our device.

Now let arping it:

$ arping -I wlan0 192.168.0.16
ARPING 192.168.0.16 from 192.168.0.14 wlan0
Unicast reply from 192.168.0.16 [7C:DD:90:1E:83:71]  84.565ms
Unicast reply from 192.168.0.16 [7C:DD:90:1E:83:71]  7.834ms
Unicast reply from 192.168.0.16 [7C:DD:90:1E:83:71]  4.652ms
Unicast reply from 192.168.0.16 [7C:DD:90:1E:83:71]  5.264ms
Unicast reply from 192.168.0.16 [7C:DD:90:1E:83:71]  6.393ms
Unicast reply from 192.168.0.16 [7C:DD:90:1E:83:71]  4.790ms
Unicast reply from 192.168.0.16 [7C:DD:90:1E:83:71]  12.274ms
Unicast reply from 192.168.0.16 [7C:DD:90:1E:83:71]  8.041ms
Unicast reply from 192.168.0.16 [7C:DD:90:1E:83:71]  6.286ms
Unicast reply from 192.168.0.16 [7C:DD:90:1E:83:71]  5.045ms
Unicast reply from 192.168.0.16 [7C:DD:90:1E:83:71]  5.012ms
Unicast reply from 192.168.0.16 [7C:DD:90:1E:83:71]  6.834ms
Unicast reply from 192.168.0.16 [7C:DD:90:1E:83:71]  4.571ms
Unicast reply from 192.168.0.16 [7C:DD:90:1E:83:71]  9.275ms

So the issue is related to ICMP (ping) but ARP is fine.