CDP confusion

Unanswered Question
Feb 22nd, 2009
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Can some one post the link or good documentation where I can find information about how CDP works and what i can do with the help of it? How CDP learns the hostname of remote devices and all?


Devang Patel

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Harold Ritter Wed, 02/18/2009 - 06:51
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There is not interaction between the hostname resolution used by the router and the hostname received via CDP. So you can't use the CDP hostname to telnet to the remote device unless this hostname is also configured in your DNS or locally on the router using the "ip host" command.


devang_etcom Sun, 02/22/2009 - 18:16
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Thanks for your input! I had some strange situation in switching environment, under show cdp nei details I was able to see the IP address of VLAN interface but when I tried to telnet it I wasnt able to do that but when I tried using device name I was able to. but the hostname bind to different IP address in DNS system. Finally i did trace route and I found router is trying to telnet the CDP neighbor via WAN link not the directly connected ethernet where it learned neighbor using CDP... so that stuff create confusion in my mind!

thanks again!

Devang Patel

Leo Laohoo Sun, 02/22/2009 - 17:33
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Configuring Cisco Discovery Protocol on Cisco Routers and Switches Running Cisco IOS

Hope this helps.

devang_etcom Sun, 02/22/2009 - 17:55
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Thanks all of you for links! so here we can see the neighbor IP address as well as host name! so I can telnet to device using hostname also there I dont need to have any kind of DNS name server configuration to resolve right? as CDP is learning it using the TLV! right!!!


Devnag Patel


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