Able to see switch through CDP, but can't ping/telnet

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Jun 29th, 2007
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We are having connectivity issues with a couple of our 3750 switches. The devices were working a week ago but now we can't connect remotely or ping. Switches are showing up in CDP neighbors. Any ideas of what could have happened, or how to fix them remotely?

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glen.grant Fri, 06/29/2007 - 06:01
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If you cant get to them then you have to go in thru the console to look at the parameters . Check for things like no exec-timeouts on the vty's that would tie up all the vty lines.

guruprasadr Fri, 06/29/2007 - 06:15
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HI, [Pls Rate if HELPS]

Was there any Changes in the Configuration recently. Other than CDP neighbors Updates, Do you see in the "show ip route" table still the neighbors / routing Updates exists.

I hope in the CDP table you are seeing the previous History only. Can you please check again by clearing the CDP Table. Use "Clear cdp table" in the privileged EXEC mode.

Then Execute the "show cdp neighbors" command. (or) even turn OFF the CDP globally using "no cdp run" & then turn ON after few minutes in the Switch.

At last, if nothing work fine then you will have to try connecting via Console Access to Check what is happening....

If possible can you pls post the Configuration.

Hope this Helps you


Best Regards,

Guru Prasad R

srimural Fri, 06/29/2007 - 07:41
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CDP works at Layer 2, I doubt the L3 is not UP or something blocking it. If your can share the configs that will be great.

Thanks and Regards,


guruprasadr Sun, 07/01/2007 - 20:21
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I accept the suspection of Sri.

CDP works at L2 but if the IP Layer is not UP means you can't take the control of the Device.

Can you post your Configuration to investigate more on this.

Best Regards,

Guru Prasad R


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