We have several remote sites connecting back to a central site through AT&T's switched metro ethernet service, CSME. We have several CSME connections at the central side, each providing 100 Mbps bandwidth to about 10 sites each.
Recently, they're having us convert over to a new service, Opt-E-Man. Since, some of the central site connections were not set up correctly in the beginning, the existing central side connections are needing to have the sites they serve moved elsewhere temporarily so they can be reconfigured. This process is underway, but we're running into a problem. Two of the sites which were moved temporarily and have been moved back are losing connectivity for periods of time (these sites are now Opt-E-Man sites). They come and go seemly randomly. As far as I can see, nothing is being changed on either side.
When the sites become unreachable from the central side (pings are failing), I can still connect to other sites served by the same central side connection and get to the "unreachable" site. Once on the "unreachable" site, everything looks fine. The default gateway is set correctly (but can't be pinged), the results of 'show ip eigrp neighbors' seems fine. And then suddenly, without changing anything, that site will return to normal.
AT&T is not considering this to be a problem on their equipment. The configuration on our equipment is basically exactly the same as it's always been. Two sites have problems, and others have no problems at all.
Is there some way I can prove it is AT&T's problem or if it is on our end?