Re: [school-discuss] LTSP and school-provided networks on same physical infrastructure

[Don Christensen <djc@xxxxxxxxx>]

Daniel Howard wrote:
> At 12:27 PM 6/30/2005, you wrote:
>
> > Look into the capabilities of your switches.  If they support 802.1q VLAN
> > trunking, then you can create a teacher's VLAN and a thin client VLAN.
> > (VLAN means Virtual LAN, and is like having a separate subnet.  Packets
> > sent out over a VLAN trunk have a special tag in front indicating the
> > VLAN.)
> >
> > With proper configuration of your router (assuming it also supports VLANs),
> > it can route between the subnets.  By the way, you could even use a Linux
> > box as a router between the two VLANs.  Linux has VLAN support, I believe,
> > or you could use two network cards and not even have to worry about VLANs.
>
>
> The switches are probably 5-6 year old Cisco's (don't know the model number 
> off hand), but that time frame would be right given the classroom PCs are 
> running Win95/Win98.  I suspect they don't support 802.1q.  Probably also 
> the routers. 

It's certainly possible they support 802.1q.  Check the docs or let me
know the model numbers.  (Actually, looking at docs for some of the older
Catalyst switches, they all seem to support VLANs.  The really old ones
might only support ISL and not 802.1q, but that would be okay if you have
a Cisco router).

> Would every switch in the network physical path have to 
> support 802.1q?

Not necessarily, but it depends on your layout and where you need
which VLANs.

> Would it be best to use switches from all the same
> manufacturer to guarantee compatibility? (we've had issues with wireless 
> access cards from one manufacturer not working well with encryption-on with 
> a wireless router from another manufacturer.)

If you had any problems with interoperability, it would be a bug in
the equipment.  Not to say that it couldn't happen, but I would be
surprised.  Wireless is a different beast, since companies seem to
try pushing the specs to differentiate themselves.  The encryption
stuff can be especially tricky between manufacturers.

> Too bad we can't just put a third NIC in the classroom LTSP server and have 
> it split the incoming school district traffic and LTSP traffic into two 
> separate streams, and a similar 3-NIC Linux router box/LTSP server at the 
> MDF that accepts both school district network feed and cable modem feed and 
> outputs a single stream for the 24 port switches that feed the 
> classrooms.

I'm not clear on your network layout, but a Linux box is fairly
flexible in this regard.  From your earlier description, your main
limitation is that you have only a single cat5 cable into each
classroom.  With the 802.1q approach, this cable will be an 802.1q
trunk between the switch in the classroom and a router or a Linux
box with multiple interfaces.  Each port on the switch would be an
"access port" on a specific VLAN.  You might be able to run additional
cables in your network closet and to your lab to eliminate the need
for 802.1q beyond what I described.

Here is a good article on VLANs and Linux:

  http://www.linuxjournal.com/article/7268

-Don

--
Don Christensen       Senior Software Development Engineer
djc@xxxxxxxxx         Cisco Systems, Santa Cruz, CA
  "It was a new day yesterday, but it's an old day now."