slow dhcp on 1G backbone.

[Tim Peiffer]

I echo what Brad is saying..  <OT> 1Gbps requires all 4 pairs.  If not 
all 4 pairs are available due to split pairs or other failures on pairs 
3&4, you will see that even though connected to 1Gbps port the device 
autonegotiates slowly back down to 100Mbps..  In buildings where wiring 
wasn't complete, we conviced our switch vendor to put in commands to 
limit range of auto-negotiation.    In buildings where we could not 
guarantee all 4 pairs we remove 1Gbps from collection of 
auto-negotiation as a configuration option.

In practice, 1Gbps auto-negotiation takes less than 1msec, transport 
1-2msec at the outside if attached via fiber to the enterprise backbone, 
and about 20msec to discover, offer, request, ack the lease.  When we 
had auto-negotiation problems, that would take seconds to minutes to 
resolve or timeout  (as opposed to a few msec in a correctly functioning 
network).

Regards,
Tim Peiffer

Brad Dameron wrote:
> You sure you don't have a duplex mismatch or something? I have all my DHCP servers on gig and don't see any issues. This would seem more like a network issue than a application issue. Your not using Windows for the OS are you?
>  
> Brad
>
> ________________________________
>
> From: dhcp-users-bounces at lists.isc.org on behalf of Dean Montgomery
> Sent: Thu 7/23/2009 3:36 PM
> To: dhcp-users at lists.isc.org
> Subject: slow dhcp on 1G backbone.
>
>
>
> Problem: dhcp client requests are slower when our dhcp server is running on a Gig backbone with a gig switch.  Client workstations have 100 NICs.
>
> If change the server NIC to 100 and the switch to 100 - dhcp requests are almost instant.  But we loose the benefit of having a gig backbone.  We need the gig backbone because we are running 200+ diskless workstations.
>
>
>
> --
> Dean Montgomery
> Network Support Tech./Programmer
> dmonty at sd73.bc.ca
> School District #73
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