How do I enable PING through my ISA firewall?
To turn on IP routing, follow these steps:
Click Start, point to Programs, point to Microsoft ISA Server, and then click ISA Server Management.
In the ISA Server Management console tree, expand ISAServer, where ISAServer is the name of the ISA Server that you want.
Expand Configuration, and then click General.
In the details pane, click Define IP Preferences under Additional Security Policy.
In IP Preferences, click the IP Routing tab.
Click to select the Enable IP routing check box, and then click OK.