December 2006
Intermediate to advanced
1188 pages
72h 8m
English
Content preview from Cisco IOS Cookbook, 2nd EditionBecome an O’Reilly member and get unlimited access to this title plus top books and audiobooks from O’Reilly and nearly 200 top publishers, thousands of courses curated by job role, 150+ live events each month,
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Transparent Cisco IOS Firewall
Problem
You want to use a router as a Layer 2 Firewall.
Solution
To enable a transparent Firewall, start by enabling Integrated Routing and Bridging (IRB) between to interfaces:
Router1#configure terminalEnter configuration commands, one per line. End with CNTL/Z. Router1(config)#bridge1protocol ieeeRouter1(config)#interfaceRouter1(config-if)#FastEthernet0/0bridge-groupRouter1(config-if)#1interfaceRouter1(config-if)#FastEthernet0/1bridge-groupRouter1(config-if)#1exitRouter1(config)#bridge irbRouter1(config)#bridge1route ipRouter1(config)#interfaceRouter1(config-if)#BVI1ip addressRouter1(config-if)#172.25.1.101 255.255.255.0no shutdownRouter1(config-if)#endRouter1#
Next, you have to configure the Firewall inspection rules and ACLs:
Router1#configure terminalEnter configuration commands, one per line. End with CNTL/Z. Router1(config)#ip inspect nameOREILLYtcpRouter1(config)#interfaceRouter1(config-if)#FastEthernet0/0ip inspectOREILLYinRouter1(config-if)#exitRouter1(config)#access-list111deny tcp any host172.25.1.102eqRouter1(config)#23access-list111permit ip any anyRouter1(config)#access-list112deny ip any anyRouter1(config)#interfaceRouter1(config-if)#FastEthernet0/0ip access-group111inRouter1(config-if)#interfaceRouter1(config-if)#FastEthernet0/1ip access-group112inRouter1(config-if)#endRouter1#
Discussion
Beginning with IOS Version 12.3(7)T, Cisco introduced the concept of an IOS-based Layer 2 or transparent ...
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O’Reilly covers everything we've got, with content to help us build a world-class technology community, upgrade the capabilities and competencies of our teams, and improve overall team performance as well as their engagement.Julian F.
I wanted to learn C and C++, but it didn't click for me until I picked up an O'Reilly book. When I went on the O’Reilly platform, I was astonished to find all the books there, plus live events and sandboxes so you could play around with the technology.Addison B.
I’ve been on the O’Reilly platform for more than eight years. I use a couple of learning platforms, but I'm on O'Reilly more than anybody else. When you're there, you start learning. I'm never disappointed.Amir M.
I'm always learning. So when I got on to O'Reilly, I was like a kid in a candy store. There are playlists. There are answers. There's on-demand training. It's worth its weight in gold, in terms of what it allows me to do.