sujiannming at gmail.com
Wed May 2 14:16:09 UTC 2007
On 5/2/07, Glenn Satchell <Glenn.Satchell at uniq.com.au> wrote:
> 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.
Yeah, this sounds like our deployment on size and scale. I'm assuming
you change the lease to 30 seconds just for these reboot cycles,
> Of course the PABX then struggled as all the phones downloaded
> configuration files as the second part of the boot.
Yeah, I've been asking various tftp server mailing lists similar questions.
> This was a rare event, and had we just used addresses on the default
> vlan would have been fixed much more quickly.
We solved the free lease problem by multinetting a private subnet on
the native/PC vlan, and using the "allow members of voip-phones"
directive in the pool definition, where "voip-phones" is defined by
class and subclass.
> In normal circumstances we used a 1 week lease for the phones and the
> trickle of renewals was never a problem.
Did you guys run into a scenario where the phones wouldn't accept
lease times less than 24 hours? This was really annoying when using
the ISC DHCP failover configuration because of the MCLT.
"I have to decide between two equally frightening options.
If I wanted to do that, I'd vote." --Duckman
"The system's broke, Hank. The election baby has peed in
the bath water. You got to throw 'em both out." --Dale Gribble
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