Switching Question on CCNA Exam

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Apr 19th, 2007
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I have taken the exam a couple of times and have seen a question that gives me trouble. I recall only that it involves finding an IP address for a specific router or an IP address of the equipment attached to a specific port. I only know of "show arp" and "show run" commands to see IP addresses. I typed the show arp command but didn't see the IP. I am thinking that I should have typed "show run" and maybe I would have seen the default gateway IP. Are there any that I am missing?

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Michael Stuckey Thu, 04/19/2007 - 13:07
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I feel this question is vague.

If we are in Cisco equipment most likely CDP is on. This will allow you to find the IP address of connected equipment.

Just by doing a "show ip cdp neighbor detail".

If you are looking for other hosts off of a switch with the combination of "show arp" and "show mac-address-table" hopefully I spelt it correctly you can find IP addresses and ports/interfaces they talking through.

If you just need the IP's on the device you are on, the best way to do that is "show ip interface brief".

These are just some ways I thought of at the moment.

If this helps, any at all, please give me some credit. It gives me a boost!!!Ha! Ha!



radel1207 Thu, 04/19/2007 - 13:10
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Another way of looking is "show cdp neighbor". This will only work if the router or switch you are looking for is a Cisco device and CDP is enabled on each sides.

Michael Stuckey Thu, 04/19/2007 - 13:12
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Show CDP neighbor will not give you the IP address



Yes it will, if you add detail to the end

Show cdp ne det


Device ID: 2811-221.ci.henderson.nv.us

Entry address(es):

IP address:

Platform: Cisco 2811, Capabilities: Router Switch IGMP

Interface: Serial5/5:0, Port ID (outgoing port): Serial0/0/0

Holdtime : 139 sec

Version :

Cisco IOS Software, 2800 Software (C2800NM-ADVIPSERVICESK9-M), Version 12.4(8), RELEASE SOFTWARE (fc1)

Technical Support: http://www.cisco.com/techsupport

Copyright (c) 1986-2006 by Cisco Systems, Inc.

Compiled Mon 15-May-06 14:54 by prod_rel_team

Michael Stuckey Thu, 04/19/2007 - 13:16
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If you read the very first reply you will see that I stated that.

These are to very different legal commands.



jcrussell Thu, 04/19/2007 - 16:04
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I don't think "show ip cdp neighbors detail" is a valid command. It doesn't appear in the 12.4 master command index, and I get this when I try it on both a 12.4(4)T and a 12.3(15b) router:

Router5#sh ip cdp ?

% Unrecognized command

Router6#sh ip cdp ?

% Unrecognized command

Master index:


12.4 "show cdp neighbors" reference:


I think the correct command is "show cdp neighbors [type number] [detail]", with interface and detail being optional.

Michael Stuckey Fri, 04/20/2007 - 04:44
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You are absolutely right! I should not have had the "IP" in the command line. Good Catch you deserve points for that. IP was never used! Especially since this is a Cisco layer 2 command.

Keep us straight by doing the research and testing all the commands we say should work.




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