....[a good point:] "Isn't BGP supposed to work around this sort of thing?" This comes down to a little more than just "depeering" -- at least in the BGP sense. There's active route filtering going on as well if connectivity is dead" Internet Health Report is showing the L3 - Cogent peering as down.
"It's sure causing a few headaches here.(from level3 looking glass) Show Level 3 (London, England) BGP routes for 220.127.116.11
No matching routes found for 18.104.22.168
As of 16:22 BST, Level3 still seems to have no routes for cogent's space. "
Wednesday, October 05, 2005
From a blind source and the NANOG list, Level(3) has stopped peering with Cogent. "A couple weeks later than expected, but as of Oct 5 02:51AM EDT it looks like 3356 and 174 are no longer reachable."