6. ISA Server forwards the
client??™s credentials to the
OWA server.
4. ISA Server responds to
HTTP request on external
interface of 63.240.93.138
and serves up forms-based
authentication page to client.
Internal Net
Internet
2. DNS Server on Internet
informs client that
mail.companyabc.com is
the IP 63.240.93.138.
2
3
4
5
8
6
7
3. Client attempts to connect
to HTTP port of
63.240.93.138.
1
FIGURE 12.12 Explaining OWA publishing with ISA Server 2006.
gives tribute to the tight integration Microsoft built between its ISA product and
Exchange product.
An ISA server used to secure an OWA implementation can be deployed in multiple scenarios,
such as an edge firewall, an inline firewall, or a dedicated reverse-proxy server. In all
these scenarios, ISA secures OWA traffic by ???pretending??? to be the OWA server itself, scanning
the traffic that is destined for OWA for exploits, and then repackaging that traffic
and sending it on, such as what is illustrated in Figure 12.12.
NOTE
There are a few differences in setup and configuration of a deployment scenario where
ISA is in the DMZ of an existing firewall.
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