I've got a 7750 as my core router and 1GB connections to 9 sites with 7450 routers. 7 of the connections work and 2 do not. As far as I can tell, the configs are all the same (other than IP addresses) but all four of the ports show as down with port states Blocking. STP is disabled on all four ports. If I disable and then enable the ports, they go down immediately. As far as I know, the AT&T links between the sites are all good. Suggestions?