slow dhcp on 1G backbone.

[Chuck Anderson]

On Tue, Jul 28, 2009 at 12:09:19PM -0700, Dean Montgomery wrote:
> 
> ----- "Blake Hudson" <blake at ispn.net> wrote:
> > Can you try putting a hub or linksys switch (whose ports come up
> > basically instantly) between the PC and your HP switch to see if that
> > speeds up the DHCP process?
> 
> We tried putting a 10/100 HP unmanaged switch between the managed 
> switch and the client.  This made dhcp requests instant with no 
> delay.  So the managed switches are doing extra negotiation when the 
> client machines reset their link which delays dhcp.

Yes, it is called Spanning Tree Protocol.  Switches usually have a 
feature to reduce this delay called "edge" or "portfast" or "fast 
start" or similar.  You set this option on all edge ports that connect 
directly to clients and not other managed switches, and they'll start 
forwarding traffic as soon as the link comes up or at most 15 seconds 
later.