When you configure Internet Security and Acceleration (ISA)
Server, secure network address translation (SecureNAT) and the Firewall service
may not work correctly.
This issue may occur if either of the following conditions
is true:
- Your ISA Server computer has a single network
adapter.
-or- - Your ISA Server computer has a dual network adapter
configuration, and both adapters are configured on the same network
subnet.
When either of these conditions is true, SecureNAT and the
Firewall service do not work correctly, because the ISA Firewall service is
designed to work only with a dual network adapter configuration and with each
adapter configured on a different network subnet.
To resolve this issue, do one of the following:
- If your ISA Server computer has a single network adapter,
install a modem on the computer. Without this added interface, the Firewall
service does not function.
- If your ISA Server computer has a dual network adapter
configuration with both adapters on a single network subnet, configure each
network card to reside on its own network subnet. This configuration is
necessary for SecureNAT and the Firewall service to work correctly, because
before ISA Server permits SecureNAT and firewall functionality, it verifies
that the subnets of the network adapters are separate.
Note If you try to configure the two network adapters with addresses
from the same subnet, but you enter one of the addresses in the Local Address
Table (LAT) to make it appear as the internal network adapter, and you keep one
address out of the LAT to make it appear as the external adapter, the Firewall
service does not work. For example, assume that you configure one network card
with an IP address of 192.168.0.1, and you put that address in the LAT. Then,
you configure the second network card with the IP address of 192.168.0.2, and
you keep that address out of the LAT. In this scenario, ISA Server still
recognizes both of the addresses as internal.
This
behavior is by design.
For additional information about ISA Server, visit the
following Microsoft Web site:
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