Hi

Whilst investigating a different network problem using wireshark, I have noticed that our Vigor2862 router is broadcasting what appear to be invalid ARP responses every 10 seconds. Specifically, the broadcast ARPs include opcode 0x0200, which, according to wireshark at least, is undefined. Presumably the opcode should be 0x0002 (response)? Is there a missing/extra htons() in the router code somewhere or is the 0x0200 opcode a Draytek extension?

Not sure it's necessarily doing any harm although if the point of these periodic broadcast ARP responses is so everything on the network knows the hardware address of the router then something doesn't seem quite right. Anyway, thought it worth mentioning in case it is useful.

The router is currently running 3.9.5_BT and is configured to use VLAN VIDs to create two separate LANs on a connected managed switch. From what I can see, the malformed ARPs are present both after the connected switch after the VLAN VIDs are stripped off and on one of the router ports configured for untagged packets.

Kind regards

Tim

Hi Tim,
Thanks for the reply, as it has given me a few ideas. I haven't used Wireshark to confirm invalid ARP responses as I didn't have long to set up due the rest of the family's internet needs!
I will be looking at again as soon as I can so will post on here when I find out what is wrong. One again thanks for your reply.
Kind regards
Brian

That ARP broadcast is specific to DrayTek devices, it's how the External Devices menu and AP/Switch management locates other DrayTek routers, switches and APs on the same network/broadcast domain. It's been there since long before 3.9.5 firmware.