Doug Senalik's Blog — Things that aren't on the internet yet

We have some WRT54GL routers running OpenWRT Linux, and modified to record temperatures with 1-Wire sensors in the greenhouse. There is no wired network there, so we need to use the UW Wireless network that is available. There is a hard to find page with information about setting up WiscVPN on linux here: http://kb.wisc.edu/helpdesk/page.php?id=9120

But when connecting to DoIT VPN, the connection drops after about 30 minutes, and cannot be reconnected for another 45-60 minutes.

The connection drops when DHCP renewal occurs, and appears to only work again when the DPD (Dead peer detection) times out and declares the peer dead. I say this because if you disable dead peer detection, you are locked out for the entire day.

This web page had an answer: http://svn.dd-wrt.com:8000/dd-wrt/ticket/973

Add this firewall rule to /etc/firewall.user

# Rule to prevent VPN dropping when DHCP is renewed
iptables -I INPUT -p udp --dport 68 -j ACCEPT