I have an ADSL router running in "bridge mode" and a m0n0wall firewall behind that is running its DHCP client on its WAN port, where the ADSL router is connected to.
I get regular arp errors in the log like this:
last message repeated 2 times Nov 13 10:57:37 last message repeated 4 times Nov 13 10:56:40 last message repeated 3 times Nov 13 10:56:07 kernel: arplookup 0.0.0.0 failed: host is not on local network
and then, all computers from the LAN are not able to connect to the Internet anymore.
My internet service provider told me not to use the bridge mode, but I need it, to be able to do access the firewall from outside to maintain it.
I read here about configuring a packet filter. But I am not sure what is meant: is the FW getting arp requests for the IP 0.0.0.0 and does it help to drop such requests? Is it still possible that this arplookup is related to the internet connection loss?
Appendix 1: a reboot of the firewall brings the internet connection back. But this has to be done several times a day.
Appendix 2: to make sure the connection is not suffering from using 100% of its bandwith by some computers on the intranet I disconnected all other computers during internet loss and just connected my own to check the firewall state. The inernet connection could still not be re-established.