RE: [K12OSN] PXE boot problems...........resolved

[R P Herrold <herrold owlriver com>]

On Tue, 5 Mar 2002, james wrote:

> OT:  I don't see why an extra hub (You mean, a regular 10 or 100 or
> 10/100 Megabit hub?  Not a switch or router?) would interfere.
> 
> Hubs are dumb, they just boost signals and repeat everything told to
> them.  They shouldn't interfere with any network operations.  

Of course they interfere -- they add latency, and cannot
detect, and can hide collision traffic -- the so-called 5-4-3
rule of thumb -- end to end, 5 segments max, with 4 hubs max,
and no more than 3 segments occupied -- was probably in play

-- more of any of these limits can mask errors which logic
says cannot be happening, down at the physical layer.

Adding a bridge, or a switch for layer 2 regeneration, or a 
router for layer 3 can help, but MAC layer traffic cannot be 
routed (such as the PXE broadcasts) at layer 3.

Me ? -- I strive to 4-3-3, to be on the safe side.  I had a
hubbed speed mismatch negotiaion biting me just last week with
a Cisco <==> Linux 2.4 kernel/(3com or Intel) dual speed NIC
transition -- a utility dual speed switch was dropped in, and
the issue went away.

-- Russ Herrold