This is from the actual doc and should be self-explantory. The RPC over HTTP client machine must be able to resolve the name of the Exchange server to the name that is on the server's Web site certificate and the name of the Exchange Server machine. Recall that the name we assigned to the Web site certificate on the OWA server is owa.msfirewall.org. The Outlook RPC over HTTP client machine must be able to resolve this name to the IP address on the external interface of the ISA Server 2004 firewall that listens for incoming requests to the Exchange server. In our current example, this is 192.168.1.70. In addition, the RPC over HTTP client must be able to resolve the actual name of the Exchange Server to the IP address on the external interface of the ISA Server 2004 firewall used in the Web publishing rule. For example, if the name of the machine on the internal network is exchange2003be.msfirewall.org, then the external client must be able to resolve this name to the IP address on the external interface of the ISA Server 2004 firewall. In a production environment, you should have a split DNS infrastructure that correctly resolves names for both internal and external network clients. We have not created a split DNS infrastructure in our example, so we will use a HOSTS file to resolve owa.msfirewall.org to the correct IP address. Perform the following steps to create the HOSTS file entry on the e-mail client machine: 1. Right click Start and click Explore. 2. Navigate to <system_root>\system32\drivers\etc and open the HOSTS file in Notepad. 3. In the HOSTS file, enter the following lines under the localhost entry: 192.168.1.70 owa.msfirewall.org 192.168.1.70 exchange2003be.msfirewall.org Ensure that you press ENTER after you complete the line so that the insertion point is under the new line. Otherwise, the new entry won't be recognized. -----Original Message----- From: Steve Moffat [mailto:steve@xxxxxxxxxx] Sent: Tuesday, February 22, 2005 7:09 PM To: [ISAserver.org Discussion List] Subject: [isalist] RE: RPC over HTTP Client Host Entries http://www.ISAserver.org Which one of Tom's numerous note's would that be in relation to??? -----Original Message----- From: Andrew English [mailto:andrew@xxxxxxxxxxxxxxxxxxxxxx] Sent: Tuesday, February 22, 2005 9:06 PM To: ISA Mailing List Subject: [isalist] RPC over HTTP Client Host Entries http://www.ISAserver.org Hi, In Tom's notes it mentions you need to add the following entries to your clients host file: 192.168.1.70 owa.msfirewall.org 192.168.1.70 exchange2003be.msfirewall.org The IP's he is using are the IP addresses on his ISA External NIC. My question is if I am using say a Router to connect to the net which has a static IP assigned to it, and all the traffic is being forwarded to ISA from this router, do I use the internet IP or do I use the external LAN IP address on ISA? Toms example of 192.xxx.xxx.xxx is a LAN class IP so it can be confusing. ;) Thanks Andrew ------------------------------------------------------