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AT&T U-verse 2wire Gateway and DD-WRT Router in DMZ Mode…
We’ve recently upgraded our ISP to AT&T U-verse. With this switch AT&T provided a 2wire gateway. So far the service has been excellent. Recently we setup a live chat support feature on the website, as you can see to the right. With this feature we also plan to integrate a remote desktop feature, to allow us to provide our clients with live and instant support.
While setting up our new live services, it became apparent that we would need an external IP address issued to our WRT54GL router running DD-WRT. Our first attempt led to success, but our connection was dropping every 10 minutes. This was causing our dowloads to drop and fail, IM disconnects, and live support dropping our support sessions. After reading the router logs, we found that our WAN DHCP lease was running out after 10 minutes. After that 10 minute time frame the connection was dropped, and the lease renewed. Obviously this is a major problem.
With a bit more research we found that the DD-WRT SPI firewall is blocking responses from the DCHP server. UDP requests are sent to the DHCP server at 50% intervals, but the response is actually coming from a different server, and is thus blocked by the firewall.
The easiest fix for this is to add the following command to your firewall rules.
iptables -I INPUT -p udp --sport 67 --dport 68 -j ACCEPT
After entering this command into our firewall rules, our issues with dropped downloads, and intermittent web signals vanished. It ended up just being a case of a powerful firewall, doing its job just a little to well.
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