ICMP Requests

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Feb 18th, 2009
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I am trying to configure a Cisco 2600 series router with the ability to respond to ping requests no matter if the devices are online or not. I would like the person performing the ping request to believe that the devices are alive on our end--that each IP in the entire subnet range should reply back. Is this possible?

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Mohamad Qayoom Wed, 02/18/2009 - 12:34
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I don't think that a device can reply to ICMP requests when it's offline.

jerrydurden Wed, 02/18/2009 - 12:44
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I understand that a device can't reply if its offline. I simply want any ping request to be replied to regardless if the device is online. Thanks for the reply.

2go2marketing Wed, 02/18/2009 - 12:49
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You are probably confusing people with what you are saying. Can you please clarify? Are you trying to get responses like "Destination host unreachable" or "request timed out"? Because you won't get any other responses from what you are requesting to do.

John Blakley Wed, 02/18/2009 - 13:04
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I think I understand your end result. What he wants to do is have the router respond to icmp packets like the device is online. So, if someone pings, and doesn't really exist, he wants them to THINK it's a live host.

I'm not sure this can be done though, but I'm going to follow this thread to see if it can.


paolo bevilacqua Wed, 02/18/2009 - 13:04
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Jerry wants to positively reply pings on behalf of other devices, while leaving their other functionality unchanged.

I haven't tried that but with an extended ACL it might be doable.

ip nat inside source list 101 x.x.x.x

ip nat inside source list 102 x.x.x.x

ip access-list extended 102 permit icmp echo-request ...

These are not the exact commands, just to give an idea of where to look.


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