[c-nsp] Campus Network Design advice

[Arie Vayner (avayner)]

Marc,

I would guess that the decision would mostly be related to whether you
have a requirement to have L2 direct connectivity between the buildings.

I would suggest to try and avoid spanning L2 VLANs beyond the
distribution, and run pure L3 between DIST-CORE devices.

If you do require L2 connectivity between the buildings you could
consider using MPLS capable distribution devices (for example 7600) and
run some L2 MPLS PW's for specific applications which require the L2
connections between buildings.
If this is too complex (usually the case in smaller deployments), then
you could also look at QinQ solutions between the buildings for specific
VLANs.

Arie

-----Original Message-----
From: cisco-nsp-bounces at puck.nether.net
[mailto:cisco-nsp-bounces at puck.nether.net] On Behalf Of Marc Archer
Sent: Wednesday, January 28, 2009 03:50
To: cisco-nsp at puck.nether.net
Subject: [c-nsp] Campus Network Design advice

Hi Guys,

I'm looking for some advice on redesigning our campus network.

We have around 2500 devices on our site which are spread across multiple
buildings. At present the network runs on a (legacy) single flat VLAN
which has caused us more than our fair share of headaches of late.
Basically we are looking at 2 design options :

The first option we have considered is to have a "router on a stick" at
our core and trunk VLANS out to distribution switches in each building
(and on to workgroup switches etc), leaving all routing to be done at
the core. This would allow us to have all VLANS available in each
building but I'm not sure if this is still going to be a problematic
design (with VLANS extended all over the site).

The other option we have been looking at (see attached) is to have L3
switches as all our distribution switches and contain VLANS to a
particular building. This seems to be a neater solution to me, but I'm
not sure of the best way to connect the distribution switches back to
the core. I would also like to connect adjacent distribution switches
together for redundancy, so I'm wondering if I should be looking at a
heap of /30 links between distribution switches & the core (and run
OSPF) - or just use a L2 network and let STP manage the links.

I havent had much playtime on networks this size so any advice would be
greatly appreciated.

M.