Outlook Clients behind ASA disconnect from Public Exchange

[michoco911]

Hello,

We have a setup where clients on the internal network send/receive their emails through Microsoft Outlook client, while the Exchange server is hosted on the internet, outside the organization.

The clients are connected to a Cisco switch, behind an ASA5510 Firewall. The Firewall is connected to an internet router, with double NAT (On the ASA and Router).

the outlook clients disconnect from the Exchange server, sometimes for hours, and then reconnect again. During these disconnections, the same client PCs are able to browse the internet normally. There are no restrictions for the traffic going from the inside to the outside. During the disconnections, if we try to connect using a public IP bypassing the ASA & router, it will work.

Any idea about what might be the problem as it is happening frequently?

[Shrikant Sundaresh]

Hi,

Could you please run captures on the ASA for traffic to and from the exchange server, when this disconnection takes place?

access-list capacl permit ip any host

access-list capacl permit ip host any

capture capin access-list capacl interface

capture capout access-list capacl interface

show cap capin/capout to see captures.

Do you see any differences in the captures? This will confirm whether packets are being dropped on the ASA.

Also, try doing a traceroute on the PC to the exchange server, during the disconnection, to see till where the packet reaches, and compare it against the working traceroute. That will help isolate where the problem is.

-Shrikant