Why users are unable to connect to internal IM through 1 particular gateway?

Admin_Stooge used Ask the Experts™

It seems that one of our remote gateways do not allow remote users to establish a connection to their MS Communicator Client.
Lets call this gateway 'West'
"You have been signed out of Communications Service because that service has been temporarily shit down.  Please try again later."

Now if the users connect to another gateway called 'East' they can connect just fine to MS Communicator.

We have a another installation of LCS 2005 SP1 within another domain.  When I test going through the 'West' gateway I receive the following message:
"The was a problem verifying the certificate from the server.  Please contact your system administrator"

So is it something with the 'West' gateway or the LCS servers not allowing access when authenticated through the 'West' gateway?

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It sounds like the 'West' gateway has an access-list applied to the interface you're traversing which is blocking the traffic. Both the IM failures and the certificate authentication issues may be related to this same issue, an ACL on a router interface.

Do you have access to that device and if so, would you be able to verify and/or modify the ACL?


No ACL applied. If you do a packet capture, you actually see the “401 Access denied” error coming back from the LCS server.
Although you didn't specifically say it is, adding this question to the VPN group begs the question - are these two connections going through a VPN? If so, make sure the ACLs allow the same types of traffic and the encryption domains are correct.
The VPN gateway  is behind a firewall which was doing a deep inspection on the SIP packets.
It was disabled and it’s fine now.

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