December 2006
Intermediate to advanced
1188 pages
72h 8m
English
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Redirecting ICMP with HSRP
Problem
You want to enable ICMP redirects with HSRP.
Solution
In older IOS releases, when you enable HSRP on an interface, the router will automatically disable ICMP redirection. However, starting with IOS Version 12.1(3)T, Cisco has changed how ICMP redirection works with HSRP, and it is now enabled by default.
You can explicitly enable ICMP redirects on HSRP-enabled interfaces with the following commands:
Router2#configure terminalEnter configuration commands, one per line. End with CNTL/Z. Router2(config)#interfaceRouter2(config-if)#FastEthernet 1/0standby redirects enableRouter2(config-if)#exitRouter2(config)#endRouter2#
The following commands prevent the router from the sending ICMP redirects on HSRP-enabled interfaces:
Router2#configure terminalEnter configuration commands, one per line. End with CNTL/Z. Router2(config)#interfaceRouter2(config-if)#FastEthernet 1/0no ip redirectsRouter2(config-if)#standby redirects disableRouter2(config-if)#exitRouter2(config)#endRouter2#
The unknown keyword allows you to use ICMP redirection to nonHSRP routers:
Router2#configure terminalEnter configuration commands, one per line. End with CNTL/Z. Router2(config)#interfaceRouter2(config-if)#FastEthernet 1/0standby redirects unknownRouter2(config-if)#exitRouter2(config)#endRouter2#
Discussion
When a router receives a packet from a LAN interface, but the route to the destination points to another router on the same LAN segment, the router will send an ICMP Redirect ...
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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.