We have a Cisco 1720 router with a WIC-1DSU-T1 card hooked to a T1\nline and our internal Ethernet network. Access control lists\n(firewall) were recently implemented.\n\nWe have been having problems for over a week (both before and after\nthe firewall configuration) where the router apparently either loses\nits connection to the T1 or simply hangs. We aren't sure which.\n\nFirst symptom is usually that we lose any response from the internet.\nA look at the router reveals that the WIC1 light has gone out, but\nPWR, OK, and ETH ACT are still lit.\n\nThe fastest thing we have found go get things back up and running is\nto disconnect the cord from the T1 jack for about 3 seconds, then plug\nit back in. In 12-15 seconds, with WIC1 light comes back on and our\ninternet connectivity returns. Powering the router down and back up\nwill also restore connectivity, but takes a little longer.\n\nThis loss of connectivity seems to happen most often between midnight\nand 4:00 AM, also between 11:00 am and 3:00 p.m. For the last week we\nhave not gone more than 36 hours without this happening. Also,\nsometimes it happens 10 minutes apart.\n\nWe have swapped WIC cards, and even swapped routers (identical cards\nand routers) to no avail.\n\nLogging doesn't seem to reveal anything unusual, but we may not know\nwhat we need to look for, either.\n\nDoes anyone have any suggestions, thoughts, or things we could try\nwhile we still have any hair left?\n\nThanks!