In my central office I have a SonicWALL NSA-2400 appliance acting as the hub for several remote offices. It is configured to pass DHCP requests to my internal DHCP server. The VPN connection works fine, IP addresses are distributed to remote offices as they should and I'm very pleased with the results - except for one remote office.
Last Friday I installed the little brother of the NSA-2400, the NSA-240 in a remote office. Both firewalls report rock solid connectivity at all times, and all aspects of network connectivity through the tunnel are working well. My problem is that so far, each morning the remote office will call and tell me they don't have any network access. In each case, they have lost their IP addresses handed out by my corporate office DHCP server and have been given "junk" 169.xxx addresses.
Restarting their firewall and renewing their DHCP lease fixes the problem immediately. Renewing the DHCP lease without first restarting their firewall fails.
Keep Alive is enabled on both firewalls.
Clearly after some amount of inactivity, the IP addresses are expiring. Can anybody shed some light on this for me?
EDIT FOR MORE INFORMATION: At this point I have determined that the IP addresses at the remote site fail after 8 hours of uptime. The logs indicate ARP packet failures around this time. To reiterate, even after the 8 hour mark, the tunnel is stable on both firewalls, only the DHCP-assigned IP addresses are lost. I restarted the remote firewall this morning at 7:45 and had them repair their connections, so I will be receiving another call from them at 4:45 telling me their internet is down.