dhcpd performance?

Glenn Satchell Glenn.Satchell at uniq.com.au
Wed May 2 12:57:17 UTC 2007

>Date: Tue, 1 May 2007 15:48:09 -0400
>From: "Jiann-Ming Su" <sujiannming at gmail.com>
>To: dhcp-users at isc.org
>Subject: Re: dhcpd performance?
>On 5/1/07, Bruce Hudson <Bruce.Hudson at dal.ca> wrote:
>> ...you should probably rethink what you are doing.
>Preaching to the choir, my friend. ;-)  Unfortunately, I don't have
>enough political clout to stop/change the VoIP deployment.  Think 1000
>phones (or more) rebooting all at once.

I have run dhcp in failover mode on two low end Sun boxes (Netra T1).
3500 PCs, 4500 Phones. When the PABX gets rebooted all the phones reset
simultaneously. This was a rare event (maybe once/year) and was always
scheduled for out of hours when possible.

The phones were spread across 6 or 7 vlans in different locations. So
about 1200-1500 phones in the largest office.

In our particular situation the phones requested an IP address on the
PC vlan, then after receiving an offer reset to the phone vlan. Our
bottle neck was that we only had 200 or so free IP adresses in the
initial vlan, so it would take up to 2 minutes for a lease to expire
after the initial offer before it could be re-offered. We tuned the
timeout value back to 30 seconds and found all the phones would be
sorted out within a couple of minutes.

Of course the PABX then struggled as all the phones downloaded
configuration files as the second part of the boot.

This was a rare event, and had we just used addresses on the default
vlan would have been fixed much more quickly.

In normal circumstances we used a 1 week lease for the phones and the
trickle of renewals was never a problem.


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