My line was down this morning, and multiple reboots of router and modem didn't work. Line tested fine from outside, and all openreach modem lights were green and solid. I noticed the NIC lights were green at both ends of the connection to WAN2 <> Modem, BUT the WAN2 light was OFF on the 2830.

Solution : In the router config, I disabled the WAN2 port, reboot, Enabled WAN2 port, reboot. Light came on, and it solved the problem. First time that's happened though.