Selection of Software for IOS Firewall Issues
To turn the router's IOS firewall on, you need a special IOS image that has the firewall feature set, which is a paid feature. Example 5-16 shows the output of the router with the IOS Firewall features.
Example 5-16 shows a Cisco 2600 router with 64 MB of RAM (60416 K + 5120 K), 16 MB of flash memory (16384 K), and a code image called flash: c2600-ik9o3s3-mz.122-15.T5.bin.