ASA seems to close connection to Messagelabs proxy

[Marcel Nobel]

Hi,

We use a Cisco ASA. We use an external proxy server from Messagelabs (Symantec). Our clients are configured to use this proxy server. Since a few weeks we are having problems downloading large files. When we talked to Messagelabs about this the confirmed the changed something in their configuration. They now first download the complete file and scan it. During the download at messagelabs it seems the ASA closes the connection. In the log I see the following:

Deny TCP (no connection) from 85.158.139.102/3128 to NIC-Public/21121 flags PSH ACK  on interface outside

Does anybody know what I change on the ASA to make this work?

Best Regards, Marcel

[Vibhor Amrodia]

Hi,

So as this Syslog might show you as well , would mean that when this PSH ACK is received on the ASA device , it does not have any established connections for the IP addresses and hence drops it.

Now , that can be because of various reasons , like possible asymmetric routing , connection timeouts etc.

I think to get to the bottom of this issue , you would need to trace the file transfer and see why this connection is being dropped in the first place.

Thanks and Regards,

Vibhor Amrodia