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Lync Troubleshooting: federation not working

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Issue

 Lync federation not working.

Error :

Test-CsFederatedPartner : A 504 (Server time-out) response was received from the network and the operation failed. See the exception details for more information.

Problem Statement:

Recently many Lync users complain regarding Lync IM not working with a federated partner. Nothing changed, however, Lync federation stopped working. When testing federation using Lync PowerShell it was giving above error.

Resolution

The resolution was very simple and straight forward. However, you must check below steps to find a solution.

  1. Try to telnet target Lync edge FQDN using 5061 port number.
  2. Test-CsFederatedPartner –Target “Lync Server Pool FQDN” –Domain “Partner Domain name” and see the result. If you get above error means something with your federation partner Lync domain issue.
  3. Try to nslookup on command prompt and type below.
    1. Set q=srv
    2. _sipfederationtls._tcp.domainname.com
    3. You will get the exact edge FQDN and verify with access edge FQDN which you configured in External access, under the allowed domain.
  4. Go to Lync Control Panel and check the Lync Edge server FQDN and Domain name.
  5. If Access Edge FQDN is not correct then change to correct one and test the Test-CsFederatedPartner command and see the result.
  6. In this case Access edge FQDN was changed from federation partner. Corrected the same and Lync federation started working.