@Qdu1 ,
Can the users in branch site communicate with internal user properly?
It seems something wrong with configuration on Edge server.
Please check the following things:
- Edge Gateway is configured on the external NIC
- DNS Points to the external DNS
- Routing entries for the internal Network are done by route add
- Edge Server can resolve the FQDN names from the internal Lync Server by host entries or DNS
- The Edge Server FQDN can be resolved by the internal Clients.
- Firewall are set correct for the needed ports
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