I've ran into a puzzling scenario and I thought I'd ask around to see if anyone else has an idea.
I have a customer who operates a server on our network who informed me that a customer of his out of Ireland is having connectivity issues to it. The ISP in question is Eircom, and the block that seems unreachable is 22.214.171.124/13.
Any trace to an IP in that block drops off the Earth at the edge of the Tier 1 provider that we connect with, such as AT&T and Sprint. I've also tried Level3, but the traffic goes over to AT&T in the end anyhow. I've checked Level3 and Sprint's looking glass and performs a traceroute from there, and I get the same result, so it doesn't appear to be an issue with our network.
I'm at a loss and my customer told me that his customer has already contacted Eircom and they are at a loss to explain the disconnect as well. Does anyone have some insight into this?