[cisco-voip] DHCP Migration Strategy - RFC

[Norton, Mike]

If you are concerned about side-effects of altering lease time and your scopes happen to have a lot of spare addresses, you could do it with exclusions instead. E.g. for a /24 subnet with 100 phones you could exclude .128-.254 on the old server, wait for all phones to get leases below .128, switch to the new server and exclude .1-.127 on it, wait for all phones to get leases above .127 and then remove the exclusion.

--
Mike Norton
I.T. Support
Peace Wapiti School Division No. 76
Helpdesk: 780-831-3080
Direct: 780-831-3076

From: cisco-voip-bounces at puck.nether.net [mailto:cisco-voip-bounces at puck.nether.net] On Behalf Of Lelio Fulgenzi
Sent: September-17-09 2:51 PM
To: cisco-voip voyp list
Subject: [cisco-voip] DHCP Migration Strategy - RFC

So, I'm planning on moving the DHCP service off a CallManager subscriber to our central DHCP service. Past experience tells me that this shouldn't be too much of an issue, but there are some things to look out for. For example, IP address conflicts on phones causes both phones to reset.

Here's what I'm planning on doing (testing out on one scope to begin with):

 1.  Lower lease time on CallManager subscriber DHCP server from 8 days to 1 hour. Wait until all phones have a 1 hour lease.
 2.  Change IP helper address on interface to new DHCP server.
 3.  Deactivate scope on CallManager subscriber DHCP server.
 4.  Wait one hour until all phones have new lease on new DHCP server and all IP address conflicts are resolved.
 5.  Remotely reset phones that are not co-operating.
Two questions:

 *   Is having a 1 hour lease time on the subscriber an issue? It's a 7835 from about 4 years ago and it does nothing else other than DHCP/TFTP.
 *   Can I go a step further and lower the lease time to 30min or even 15 min without significant concern?
We have about 7500 phones.
---
Lelio Fulgenzi, B.A.
Senior Analyst (CCS) * University of Guelph * Guelph, Ontario N1G 2W1
(519) 824-4120 x56354 (519) 767-1060 FAX (JNHN)
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"Bad grammar makes me [sic]" - Tshirt
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