On Sat, Jul 07, 2001 at 11:23:33AM +0200, Mikael Abrahamsson wrote:
> I thought this was accounted for in the DHCP specs, that you need to wait
> at least 30 seconds before deciding that the dhcp server is unavailable. A
> lot of network cards do not do "link-up" until the driver initialises the
> card and thus you're in the 30 second wait period when you bring up the
> link and then starts asking for dhcp servers.
IIRC, Spanning Tree takes 30 seconds to go into forwarding state in the absence
of any BPDUs, so it's a fairly close run thing if the computer is quick enough
booting. (Although it also depends on other things - such as the NIC
"blipping" the link state during driver initialisation - see below) On some
switches you also have EtherChannel Negotiation which can push the port
startup time to 50 seconds.
Some Operating Systems (Windows NT 4 seems to be one, although I suspect it was
the fault of the driver, not the OS Kernel) actually start the DHCP process
before the network card has fully initialised, so you get less than 30 seconds.
I've actually seen one extreme case (With 3Com 3C905s - both the B and the C)
where even the speed/duplex auto-negotiation phase is enough delay to cause
Windows to fail booting. It's an extreme case but it does happen. (DHCP
eventually suceeded, but the PDC/BDC search phase had already timed out)
(Specifically:
- Windows trying to find a PDC/BDC before DHCP has completed.
- DHCP trying to start before the network card has fully initialised.
- Network card driver "blipping" the link state during initialisation, causing
speed/duplex/Spanning Tree negotiation to start again.
- BDC at far end of a E1 link
Eventually fixed it by turning off all auto-negotiation and putting the PDC/BDC
IP addresses in LMHOSTS.)
-- Ryan O'Connell - <ryan@complicity.co.uk> - http://www.complicity.co.ukI'm not losing my mind, no I'm not changing my lines, I'm just learning new things with the passage of time
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