CompanyA has had trouble in the
past securing and auditing access to their email services. When the decision was made to
upgrade their existing Exchange 5.5 environment to Exchange Server 2003, a design
process was followed to further secure the environment within the confines of the existing
network and security infrastructure. The results of this design are reflected in Figure 4.8.
Exchange
Mailbox
Server
Exchange OWA
(CAS) Server
SMTP Mail
Filter
Exchange OWA (CAS)
Exchange
Mailbox
Server
ISA Server
Enterprise
Array
Exchange
Mailbox
Server
New York
Paris Tokyo
ISA Server
Standard
ISA Enterprise
Array
Internet
New York Internal Network
Clients
Clients
Exchange
Mailbox
Server
ISA Server
Reverse Proxy
for OWA New York Internal Network
New York DMZ Network
Paris Internal Network
Clients
Tokyo Internal Network
Paris Email Network Tokyo Email Network
Remote
Clients
FIGURE 4.8 Examining an ISA deployment at a large organization.
132 CHAPTER 4 Designing an ISA Server 2006 Environment
CompanyA secured access to its email environment by placing all email-related components
behind ISA servers. In New York, inbound email is sent to a SMTP Smarthost that
scans for viruses and spam and then forwards the messages to the New York Exchange
Servers behind an enterprise array of ISA servers.
Pages:
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273