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[Solved] Call failed due to network issue Microsoft lync when both endpoints are internal

While working on Microsoft Lync I have faced “Call failed due to network issue” while making audio/video calls to the users. In my environment I have successfully implemented Lync for IM, audio video conference, Auto Attend, voice mail. But calling was the issue in different scenarios.
Called failed due to network issue
I was not able to able to make calls due to ” call failed due network issue” in below scenario,
1. if user is connected Lync from home via Internet and other user is in office network
I was able to make calls if,
1. If I connected to the Office network via Remote Access VPN & other users is in office network
2. If both user are connected to Lync server via internet through Lync edge server.
But call fails if both users in the different network i.e. in office or at home
In my network we have five location & user logs in to the Lync server from different five location via site 2 site vpn or from home via Internet.
Below are the network details of five offices,
Server Network –
Office 1 –
Office 2 –
Office 3 –
Office 4 –
Office 5 –
My Microsoft Lync front end server is in the network along with my archiving, monitoring, SQL Server & Edge server Internal facing network card.
TO resolve you have to add routes for your internal network on your Lync Edge server,
My Edge server IP’s are
1. Internal Mask
No gateway
DNS – Internal DNS server
2. External Facing Network
IP – Mask
Gateway –
DNS – &
My gateway for Internal network traffic for my Edge server is ( is so that it can communicate with the Lync front end server. Same way you need add routes for your other network i.e. offices on your edge server as shown below,
Open Command Prompt on Edge Server & add routes
route add -p mask
route add -p mask
route add -p mask
route add -p mask
route add -p mask
Gateway will be the same for all other network traffic. Once you add persistent route restart Edge server & try to make calls.