I have a client who has a Cisco ASA 5512 device with, among other things, an inside interface dubbed "InternetOnly" on an internal 172.28.0.0/24 network.
They also have a single outbound interface with a small IP block in use coming in for varied usages.
Specifically, there is an external IP (x.x.x.219) that is setup to route to the local Exchange server for OWA. This configuration works without issue for all external connections coming in. Other internal networks have access to the local DNS server and resolve the Exchange server locally. This guest interface, however, utilizes DNS provided through google's external servers. NSlookup finds the correct external server for the webmail (x.x.x.219) CNAME for their domain, but will not load. I would like to keep the guest interface from contacting and internal structure directly, but am looking for a way to ensure that I can get OWA to load properly by routing through the external webmail.domain.com (x.x.x.219) address. Any thoughts on why it might not be doing so?
