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A: As with the 3Com 812 you map the public IP addresses to private ones.

Your 3Com Firewall should already be connected to your intranet and setup with the appropriate addressing scheme.

1. Private (local) address of 3Com Firewall is

2. The static (public) IP address range from SBC/Ameritech assigned to you would be: -

3. Private (local) addresses to be associated with static (public) addresses are - Note that any 5 private (local) addresses can be used and they do not need to be contiguous.

Using these assumptions will result in this configuration:

PUBLIC (static) ADDRESS -> PRIVATE (local) ADDRESS -> -> -> -> ->

Firewall/Router public address:
Firewall/Router private address:

1. Start up your favorite Web Browser (i.e. Internet Explorer, Netscape, etc. note: browser must support frames) and enter the private IP address of the Firewall: and press ENTER. This should bring up the login screen. Enter the login and password to gain access to the firewall configuration screens.

2. Click on the "ADVANCED" button. It is located down the lefthand side of the window.

3. Click on the "ONE to ONE NAT" tab. It is located along the top of the window.

4. Click on the checkbox labeled "enable One-on-One NAT" to enable it. This should make the checkbox checked.

5. We will now add the address mappings. Click on the text box field labeled "Add Range" under the column "Private Address Range Begin". Enter in the public address of

6. Enter in the private address of under the column "Public Range Begin".

7. Enter 5 for next textbox labeled under column "Range Length". Note that you can enter 1 for this if your private ranges are not contiguous.

8. Click the button labeled "update" along the righthand side of the screen.

9. The status line (located at the bottom of the window) should now say "restart Internet Firewall for changes to take effect". Click on "restart".

After the restart the 3Com Firewall should be configured for the five static (public) IP addresses.

All PCs that are connected after the firewall need to be setup using the firewall's private IP address ( as the default router/gateway and DNS server.

*** WARNING *** Servers or other devices assigned to one of the five static IP addresses are open from access to the Internet. Be sure you have adequate safeguards in place to prevent malicious or inappropriate access to these systems!

Submitted by James Newlin.

Special thanks to John Taylor and his 3Com 812 FAQ entry at »AT&T Midwest/Ameritech FAQ »Setting up 3Com Officeconnect Remote 812 Router with 5 Static IP package

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by jnewlin See Profile edited by lev See Profile
last modified: 2005-06-28 13:43:59