Network Security – Part Three

Michael Accetta

On February 13th In IP Solutions, IP Surveillance Video, IP Tech Tips, Networking

ISP Device Firewall Settings

To program the firewall in an ISP-provided DSL or cable modem, first the device’s LAN address must be determined so that it can be accessed.

To gather the router’s LAN address, technicians can use the “tracert” command in Windows from any PC within the LAN. This test will provide the LAN address of any routers between the PC performing the test and the Internet, along with all of the routers that pass the data packets over the Internet to the target web address.

To perform a tracert test, a technician should go to the command line on a Windows PC, and type in tracert as illustrated below:

Any valid Internet address can be used as the target. What we are looking for is the first one or two routers that appear on the report. In most cases the ISP DSL or cable adapter will be either the first or the second of the two routers listed in a tracert test. We can identify these devices as being on the LAN because they use a permutation of a private IP address. In the above test the first router has an address of; this is a private Class A IP address and is the LAN address for the Linksys router on my network. The second address is a Class C private address. The third address, is a Class A public address and is also identified as part of the sbcglobal – AT&T provided Internet connectivity. So the second address shown is the LAN address of the AT&T Uverse DSL adapter that connects my network to the Internet.

To access the firewall settings in the router, open Internet Explorer and put in the LAN address of the device, i.e. You should see the access page for the DSL adapter.

To enter the firewall settings screen, you will need to have the password for the device supplied by the ISP.

Once you’ve gained access to the ISP adapter, you’re ready to set up the firewall to allow authorized users to access devices such as IP cameras from over the Internet. We’ll go through those settings in the next blog post.