Subject: Re: vaxserver 3100 netbooting, nfs_boot timeout
To: Thorsten Jens <>
From: Johnny Billquist <bqt@Update.UU.SE>
List: port-vax
Date: 09/10/2000 20:16:32
On Sun, 10 Sep 2000, Thorsten Jens wrote:

> * Johnny Billquist:
> > On Sat, 9 Sep 2000, Frederik Meerwaldt wrote:
> > 
> > > > UDP  from server3100.thod:1023 to on eth0
> > > > UDP  from server3100.thod:1023 to on eth0
> > > > 
> > > > Shouldn't that be since is the
> > > > nfs+bootserver? I'm really desperate.
> > > 
> > > Your server3100 makes a broadcast, and if then your should
> > > answer! As said, it should. What does a tcpdump tell about the answer?
> > 
> > My guess is that he's using a subnet mask, and the network don't recognize
> > network broadcasts when you have a subnet...
> >
> > People seem to love to use a netmask of 0xffffff00 on net 10, for some
> > obscure reason (it cannot possibly be that they don't know any better...
> > :-)
> Hmm -- I *am* using a subnet mask of, and I honestly
> don't know what should be wrong about subnetting that way. I never
> had any problems with this setup, with no OS. Tell me why I should
> change that :-)

Thought so. :-)

The problem is that 10.x.y.z is an A-network address (I hope you forgive
me if you already know this) and the broadcast address is
In addition to this, if you are subnetting a network, you also get a
subnet broadcast address. So in your case, there are actually two
broadcast addresses: and Unfortunately, many
IP stacks ignore the network broadcast address.

I'm not sure if netword broadcasts have been demoted to a thing of the
past or not, but obviously this is your problem right now.
(I think I've seen some RFC talking about this, but my memory is really
not trustowrthy.)

Anyway, you have several options.

1. See to it that you recognize network broadcasts.
2. See to it that the VAX does a subnet broadcast.
3. Change your network mask.

Actually, give me a good reason *why* you are subnetting 10? :-)


Johnny Billquist                  || "I'm on a bus
                                  ||  on a psychedelic trip
email:           ||  Reading murder books
pdp is alive!                     ||  tryin' to stay hip" - B. Idol