For some reason after reinstalling ISA 2006 as a back firewall, you can’t reach some machines on the DMZ network. Without a long discussion for the routing reasons for this, The solution is to modify the ISA back firewall in order to disable the proxy on it.
To disable the Web Proxy filter for HTTP, do the following:
- In ISA Server Management, click the Firewall Policy node.
- On the Toolbox tab, click Protocols.
- Expand All Protocols, right-click HTTP, and then click Properties.
- Click the Parameters tab, and in Application Filters, clear Web Proxy Filter. Then click OK.
- Click Apply to update the firewall policy.