[cisco-voip] IP phone DHCP question or two

[Mike King]

Standard DHCP server practice is to reduce your DHCP lease times down to 1
or 2 minutes, shut off the old server, and turn on the new server.

Downside is that you have to wait the minimum of half your DHCP lease (or
the entire DHCP lease if your paranoid) before you can make your change.

I imagine that would hold well here too.

Practice in old subnet first.

Mike

On Wed, Feb 1, 2012 at 5:30 PM, Tim Reimers <treimers at ashevillenc.gov>wrote:

> 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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