[cisco-voip] IP phone DHCP question or two

[Madziarczyk, Jonathan]

I see no reason why that wouldn't work.  On boot the phone should issue
a DHCP broadcast which will go to the ip helper address, from there it
should dish out addresses in a range based on the ip of the default
gateway of that subnet.

 

The only problem I've ever seen is when the DHCP server/TFTP server IP
address is hard-coded into the phone itself.  From that I had to do the
123456789*0# reset on the phone to get it to forget.

 

Anyone else have a different experience?

 

From: cisco-voip-bounces at puck.nether.net
[mailto:cisco-voip-bounces at puck.nether.net] On Behalf Of Tim Reimers
Sent: Wednesday, February 01, 2012 4:31 PM
To: cisco-voip at puck.nether.net
Subject: [cisco-voip] IP phone DHCP question or two

 

Hi all -

 

What are all the options for forcing an IP phone to get a new IP
address?

 

I know of:

-          Resetting it (I think) (how does one globally reset all
phones in UCM?)

-          shut/no shut the port

-          int range (whatever to whatever) and inline power
never/inline power auto 

 

I want to switch from Cisco router based DHCP to Microsoft DHCP

 

 

My plan would be:

Disable the ip dhcp pool on the cisco router for a given Vlan/subnet

Enable the ip helper addresses

Restart the phones and they would pull IP addresses from the new DHCP
server.

 

I know Microsoft devices (aka XP, win7 workstations) tend to know their
old IP and will sometimes cause an IP conflict when changing DHCP
servers, 

even if you reboot them they sometimes conflict.

 

Do Cisco IP phones have that same problem, or once they reset do they
forget all about any IP they once had, and go get a new one from the
DHCP server

(obviously, if the DHCP server has a lease for the phone, it gets the
same IP back, but that's not the phone's doing..)

 

thanks, Tim

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