Enabling DHCP when the WAN is down...

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Hi there,

I am not sure whether it is possible or not. My DHCP server is located in the datacenter, accessible for clients over the WAN. I am looking for a solution where, if my WAN is down the clients/hosts will get the IP from the local L3 cisco switch OR router. Kindly let me know how to proceed further if at all it is possible.

Thanks in advance!

Gaurav Sharma

I have this problem too.
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Giuseppe Larosa Sun, 11/15/2009 - 00:04

Hello Gaurav,

I would look at providing a backup link to reach the datacenter.

This is certainly possible.

For setting up a dhcp server when the wan is down you should use an EEM embedded event manager that reacts to wan link failure by injecting ios command lines for the DHCP pools.

see ask the expert with Joe Clark

http://forum.cisco.com/eforum/servlet/NetProf?page=netprof&forum=Network%20Infrastructure&topic=Network%20Management&topicID=.ee71a02&fromOutline=&CommCmd=MB%3Fcmd%3Ddisplay_location%26location%3D.2cd4b0c6

you may need to copy the whole url to the broswer to open the link

However, what would happen when the wan link is up again?

Another script should clear bindings and should remove the DHCP pool

so I think the more correct solution is to provide a backup link.

Also the problem affects only PCs that are switched on when the wan is failed all other PCs should use their current lease.

Hope to help

Giuseppe

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