arping is unreliable for wireless clients?

[Karl Perkins]

Hi,

I've noticed that arping seems very unreliable for wireless clients. It's perfectly OK for wired clients, and 100% reliable. Anybody have any ideas? No clients connected to guest wifi, and I can't see any logical reason for it to behave like it does.

Here is an example...

admin@firewall:# ping -I br0 192.168.1.85
PING 192.168.1.85 (192.168.1.85): 56 data bytes
64 bytes from 192.168.1.85: seq=0 ttl=64 time=113.649 ms
64 bytes from 192.168.1.85: seq=1 ttl=64 time=8.863 ms
^C
--- 192.168.1.85 ping statistics ---
2 packets transmitted, 2 packets received, 0% packet loss
round-trip min/avg/max = 8.863/61.256/113.649 ms

admin@firewall:# arping -I br0 192.168.1.85
ARPING 192.168.1.85 from 192.168.1.1 br0
^CSent 6 probe(s) (6 broadcast(s))
Received 0 response(s) (0 request(s), 0 broadcast(s))
admin@firewall:/tmp/mnt/Main/entware/home/admin# arping -I br0 192.168.1.85
ARPING 192.168.1.85 from 192.168.1.1 br0
Unicast reply from 192.168.1.85 [48:bf:6b:1d:2c:eb] 103.053ms
Unicast reply from 192.168.1.85 [48:bf:6b:1d:2c:eb] 105.943ms
Unicast reply from 192.168.1.85 [48:bf:6b:1d:2c:eb] 117.545ms
^CSent 4 probe(s) (2 broadcast(s))
Received 3 response(s) (0 request(s), 0 broadcast(s))

admin@firewall:# arping -I br0 192.168.1.85
ARPING 192.168.1.85 from 192.168.1.1 br0
^CSent 6 probe(s) (6 broadcast(s))
Received 0 response(s) (0 request(s), 0 broadcast(s))​

Model RT-AC86U
Firmware Version 384.10
Firmware Build Sun Mar 24 21:38:40 UTC 2019 merlin@897df50
Bootloader (CFE) 1.0.0.8
Driver version wl0: Oct 2 2018 15:11:29 version 10.10.122.20 (r683106) FWID 01-10d4394f
Entware Installed/Enabled

Rgs,

Karl.

 

[ColinTaylor]

I don't know the answer to your question, but have you tried arping from another client on the LAN (br0) rather than the router?

 

[Karl Perkins]

I have Colin. Generally speaking, ping-ing or arping-ing wired-clients work perfectly from any other wired-client on the LAN. Wireless clients may appear in a wired client's arp table, but I suspect it's because they have initiated a communication from wireless to wired client. In the other direction, wired clients don't seem to be able to reliably resolve wireless clients for ARP.

I don't know if this helps? It's really odd, I know.

 

[Karl Perkins]

Does anybody have any ideas of what to try? It's really quite odd behaviour, and not unique to the latest firmware

 

[Karl Perkins]

Seems to be exactly the same issue reported here: -
https://www.snbforums.com/threads/strange-behavior-on-latest-merlin.47103/
and here:-
https://github.com/RMerl/asuswrt-merlin.ng/issues/154