[K12OSN] LTSP Setup question.

"Terrell Prudé, Jr." microman at cmosnetworks.com
Sun Oct 17 01:45:15 UTC 2004

Hello Jim,

Why not just make one large /21 and adjust your DHCP scope 
appropriately?  Say,  This would give you 
through, which is 2046 IP addresses.  You could go a bit 
further and exclude, say, the first 255 addresses from the scope 
( through  This way, you would need exactly 
one scope on exactly one DHCP server for the entire school LAN, which 
will--I guarantee you--reduce your maintenance headaches.  The reason I 
know that is that, in my district, this is exactly what we do with /20 
subnets of the range, for all of our (currently) 256 sites, and 
having one DHCP server and scope per LAN has made things much easier to 
deal with.

Your "thick clients," i. e. your Windows or locally-installed GNU/Linux 
boxes, can use your K12LTSP DHCP server.  They will simply ignore any 
options that they don't need, i. e. the TFTP netboot stuff.  I've tried 
this out with thick clients running FreeBSD, OpenBSD, Mac OS 8.1-9.2, 
Windows 98 through XP, and more than one distribution of GNU/Linux, 
including Yellow Dog Linux.  These thick clients were just happy as a 
clam using the K12LTSP DHCP server.



Jim Christiansen wrote:

> Hello Samps,
> Oh man - this is a gem for me, although I'm now asking for some 
> clarification.  I'm the teacher who is running one mixed network of 
> K12LTSP (80 boxes) with an NT domain and now a 2k or 2003 server for 
> administrators all on a new fibre backboned network - suggested last 
> spring, by many on this list (to overcome all of the 600 volt power 
> issues in the ceilings of my 
> no-conduit-toss-the-cat5-anywhere-up-there-in-the-ceiling-it'll-be-fine-kind-of-school). 
>  My technicians are way to busy to experiment on a working system and 
> come to me for "the plan".  I'm a KISS (keep-it-simple-stupid!) kind 
> of person and have said that to avoid DHCP hang ups, I wanted only one 
> dhcp server on my network and it would be the k12 server.  This way my 
> thin client will be the only boxes using dhcp, period - no problems.  
> All other boxes are static IP.  With a reference to one sheet of paper 
> (my ip number list) I can ssh or vnc into any local linux or win box 
> for maintenance - no "I wonder what the ip of that dhcp driven box is?"
> I'm not too sure what the overall benefit would be to running dhcp for 
> the administrator-vp-secretary-councelling win boxes is.  My school 
> won't have more than 254 boxes total in it for some time (years).  I 
> guess that what we would gain though is better access for notebooks 
> (gota keep the travelling big-wigs happy)  or maybe a dhcp wireless 
> access.
> Come to think about it, this would be great...  When my kids come in 
> for a week-end lan party, they wouldn't have to reset their networks 
> either.
> OK, so if my current set up is a 192.168.1.x system, and I wanted to 
> move all of the win boxes to dhcp, what would I need to do using the 
> map that Samps has given below?
> All I would need is for a 192.168.1.x/21 network
> one win dhcp server         -
> one k12 dhcp server        
> one wireless router gateway - (for 
> notebook access)
> I know that I've set up my current dhcp server at
> The /21 is what is different.
> How will the three systems acces my one IPCop gateway/firewall out of 
> the building??
> I'm excited to give this a go!
> Thanks for any advice,  Jim
> <snip>
> Terrell Prudé, Jr. wrote:
>> You're very lucky indeed, unless you're running your K12LTSP servers 
>> in the "standard" 2-NIC architecture.  Having eight DHCP servers 
>> serving the same broadcast domain can be very, very dangerous.  Yes, 
>> I know some
> snip
>> --TP
>> _____________________
> When running the domain in a private IP block (10.255 and 192.168) you
> can run as many DHCP servers as you can make subnets.
> an example:
> A network,, has 2046 usable addresses, from
> to (255 is broadcast and can't be allocated for
> other use.
> Each of four DHCP servers are set up to use as RANGE and
> DHCP server 1 is using a SCOPE of to
> DHCP server 2 is using a SCOPE of to
> DHCP server 3 is using a SCOPE of to
> DHCP server 4 is using a SCOPE of to
> No overlaps in the scopes ensures that there won't be address-clashes on
> the network.
> If you subnet using a further 1 bit, then you can have twice as many
> DHCP servers, each serving half as many clients.
> cheers
> Samps
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