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New Member

DHCP problem on wireless IP Phones


We have a wierd problem with our Wireless IP Phones. Sometimes they dont get an IP from the DHCP server (Which is the 4503 Switch) It says IP confuration failed. We have total of 234 addresses in the pool and out of which 151 addresses are used by phones, ATA's and IP Phones. When I typed the command sh ip dhcp binding on the switch it shows that it has asigned addresses all the way till x.x.x.254 and skipped some address in between. the address pool is x.x.x.20 - x.x.x.254

I typed this command on the switch:

clear ip dhcp conflict *

As soon as I did that the wireless IP phone got IP address from the switch.

Why did this happen? How can we avoid this so it does not happen again?

Thanks for the help in advance.


Hall of Fame Super Gold

Re: DHCP problem on wireless IP Phones

Looks like the IOS DHCP got a bit confused.

I would try the following:

- upgrading to latest IOS on the switch to incoprorate any potential fix in the area,

- making the DHCP pool larger.

- make the lease time shorter

New Member

Re: DHCP problem on wireless IP Phones

Thanks for the reply. Right now my pool has a mask of What should I change that to add more addresses? will work? any other suggesstions?

Do I need to change the mask on all the devices that use static IP's as well like CCM Servers, Voice gateways etc...

Thanks again


Hall of Fame Super Gold

Re: DHCP problem on wireless IP Phones

Yes, enlarging the mask as twice should be enough. Unfortunately you should change it on all devices using that network.

So you can find easier to apply the two other suggestions first, and the making the pool bigger just as last resort.

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