Also, playing with looking glasses can be helpful in understanding what's going on with BGP from the perspective of other networks. http://www.bgp4.net/wiki/doku.php?id=tools:ipv4_looking_glas... has a list, which doesn't seem to include AT&T. Going to http://www.nordu.net/connectivity/looking-glass/lg.cgi and selecting bgp and entering prgmr.com's IPv4 address isn't very exciting, in that it only lists one ASN in the path (it seems they have direct peering with Hurricane Electric, who is announcing the block that includes that IP address under their ASN). Putting in an IP address advertised under your ASN at the looking glass of a network that peers with both Hurricane Electric and Cogent might be more interesting if you manage to see routes via both.