After deploying a Lync 2013 Edge server the Access Edge service wouldn’t start.
In the Event Log > applications > Lync Server I was getting the following error
Ensure that no other program is listening to the specified port and that the IP address is valid.
I went about checking the configuration of the Edge Server
Checked Edge Server IP’s, FQDNs
Lync Topology Builder > Edge Server IP,FQDNs
Certificates just in case
The configuration all looked ok so I wondered if there was a duplicate IP address conflicting with the Access Edge IP.
So I disabled the external NIC on the Edge Server and from another server with access in the DMZ pinged the three IPs on the external NIC and the access edge IP address replied so that meant there was a duplicate IP address on the network. After little investigation where this duplicate ip was assigned it turns out the customer had this ip address assigned on another server.doh!
After we resolved the IP address issue the Access Edge server started up a treat 
Thanks
Martin
