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CoolRanch2124
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I Love Show IP Cef!!!!

Sat May 14, 2011 6:42 pm

I started becoming dependent on a command so useful it deserves a moment of silence....:)

In the past I would always use show ip route when troubleshooting routing issues...but now do i rarely use it. Show ip cef prefix will display the contents of the FIB (Forwarding Information Base), and in one output show you the source of route, next hop and outgoing interface. This is extremely efficient, especially when working on a 6500 for example with a bunch of svi's and or vrf's. That way you dont have to pull your eyeballs out combing a routing table for recursive lookups.

Dont get me wrong, I still use show ip route for some things, mainly bgp...but with show ip cef you can move through an unfamilar network pretty quickly

example:
CAT6K#show ip cef 10.108.12.29
10.108.12.28/30
nexthop 10.108.24.73 Vlan602
CAT6K#

For those who havent used it I just had to share!!

javentre
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Re: I Love Show IP Cef!!!!

Sat May 14, 2011 7:19 pm

I agree, it's great. Especially if you want to find all of the routes behind one interface when you're doing ECMP:
http://networking.ventrefamily.com/2010 ... rface.html
http://networking.ventrefamily.com

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ibarrere
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Re: I Love Show IP Cef!!!!

Sun May 15, 2011 10:45 am

Yeah, awesome command! I always forget to use it when I need it.

'

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