Hi Readers,
Sharing a unique problem that We are facing with our Lync solution, we are close to finding the solution but atleast we have found the root cause of it.
Issue is every 15 days we see netlogon error 5719 stating:
This computer was not able to set up a secure session with a domain controller in domain due to the following: The RPC server is unavailable.
and MSMQ error 19 stating:
A connection with Active Directory Domain Services cannot be established.
These two are the main errors apart from others. When these occurs new sessions to lync have problems, Online meeting start to have issues and various other issues till we restart the server.
Another things to note when this happens you can ping domain but cant access the domain shares.
On working with Microsoft & submitting lot of logs no conclusion was occurring until yesterday when it was found that issue is because all dynamic ports(ephemeral ports)were getting exhausted.
Windows Server 2008 and later use the IANA range which uses the ports between 49152 and 65535 providing 16,383 ports.
you can use the script mentioned in below link to detect if this is happening.
http://blogs.technet.com/b/clinth/archive/2013/08/09/detecting-ephemeral-port-exhaustion.aspx
you can use Netstat -ano to find which process is consuming all the ports, In our case it was rtcsrv(lync) process.
Use below command to see what all dynamic ports are allocated to the machine:
netsh int ipv4 show dynamicport tcp
To allocate more ports, which we have done as of now below is the example:
netsh int ipv4 set dynamicport tcp start=30000 num=35535
Now run the first command again you will see that there is more allocation now.
After increasing the ports We were able to access domain shares which proves that ports exhaustion was the issue ..
We are still working on if there is any issue, on why ports are getting exhausted or this is normal in our case because of usage has increased . Lets see what comes out..:)
Tech Wizard
Tech Wizard 