[c-nsp] Small DC switch design

[Jason Gurtz]

Your size sounds fairly close to our situation... Do you have a spare
fiber pair going to each location?

> Right now in each of the 7 buildings has a 3560G as an aggregation
> switch connected back to the DC.  The DC also has a few 3560G's and
> 3750G's for the sans and servers.
[...]
> What I would like to know (costs being the biggest factor) is what
> would be a better switch design for the current and future traffic in
> this network.  Some options I was thinking about are as follows:

Without more details I'm guessing here. Like many smaller shops I've been
around the thing has grown from a long time ago and there may be a
primarily flat L2 design in place, maybe there are some vlans. Maybe there
is some (or a lot of) daisy chaining of switches; maybe the spanning-tree
configuration hasn't gotten a lot of thought. OTOH, hopefully you're in a
better spot than this?

In the Cisco world I think you're right on the money with Cat45xx; the
49xx series are related... Skim over this document and see if the general
idea makes sense. You have L3 capable switches everywhere so it's a no
brainer in a way:
https://www.cisco.com/application/pdf/en/us/guest/netsol/ns432/c649/ccmigr
ation_09186a00805fccbf.pdf

We used this as a model, a pair of 4900M switches as the core and a few
4507-E w/SUP-6E as our access switches running OSPF; it is collapsed-core
w/10G links fanning out (no separate distribution layer). As a whole we
are very happy with the system. The nice thing about routing everything is
it fails in more pleasant ways than the typical spanning-tree disaster.

The 45xx line has seen a major upgrade. You probably want a "+E" chassis
instead of "-E". Also, the SUP-7E is out and it has netflow amongst other
upgrades. There is an SUP-7L-E as well for a cheaper option. Check with
your rep about bundles as it's definitely money saving. For the core, look
at the 4900M or the newer 4500-X; these two switches are basically a
semi-fixed version of the cat45xx (fixed sup, replaceable line cards).
Note with sup-7 based switches you are going to IOS-XE instead of classic
IOS. Another budget-wise choice for the core and aggregation may be the
ME3600X/ME3800X. It's marketed at the ISP space but search through the
archives of this list for discussion of it.

Even if you aren't going down the road of L3 in the access layer I can't
recommend enough making sure a hierarchical design is in place. It is much
easier to troubleshoot and changes are much easier to implement.

~JasonG