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Basic URL Filter Using CBAC


Hello All,

This document is intended to explain how to use CBAC to block http websites. The command that we are going to use is called ip urlfilter in conjunction with the Legacy Firewall (CBAC).


  • An image that Supports CBAC (Normally Advanced security or Adavanced IP services)
  • The ip urlfilter command introduced in 12.2.(15)T. 

This is the scenario that we are going to use:



  1. Create the URLfilter policy with the command IP urlfilter

Command structure

ip urlfilter exclusive-domain <permit/deny> <website_name >


ip urlfilter exclusive-domain deny

The exclusive domain will be the name of the website you want to allow/deny.

  2.  Select what to do with the sites that are not specified:

Command structure

ip urlfilter allow-mode <on/off>

This is a fail open, fail close mechanism, if it is turned on, all the rest of the websites not specified are going to be allowed, if it is set to off, all the websites will be blocked.

3.   Create the Firewall policy in order for the Router to inspect the payload and block/allow the website

Command structure

ip inspect name <name> protocol

In order to configure the urlfilter policy, we need to inspect http protocol


ip inspect name Webfilter http urlfilter

The url filter will call the filter policy that we created.

4. Apply the url filter on the interfae

Command structure

ip inspect <name> <in/out>

This is in order to set the direction on the filter. In case that you want to filter specific users on an specific interface, you will need to apply it closest to the user, if you want to configure it globally, just put it on the outbound direction on the internet facing interface.


Int fa 0/0 (Facing internet interface)

  ip inspect Webfilter out

Final configuration

ip urlfilter exclusive-domain deny

ip urlfilter allow-mode on

ip inspect name Webfilter http urlfilter

Interface fa0/0

ip inspect Webfilter out

When the customer tries to access website the user will get the following page on the web browser:

Deny message.PNG

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