Design ideas for Layer 2 backbones?

[anthonyanderberg]

For many years I've been a proponent of layer 3 based
backbones - locating subnets geographically behind
individual 8600s and using OSPF in the backbone to
provide quick failover and straight-forward link
troubleshooting. Its all worked very well, but a
number of things are on the horizon that will probably
require me to use VLAN tags to carry those subnets
to other places on the network. That seems to require
backbone links that operate at layer-2, and traditionally
redundant layer-2 backbones require my old nemesis
Mr spanning tree. - with his slow convergence times
and expensive but unused backup links.

So my question: What kinds of layer 2 backbone
designs have you folks had good success with?
I've looked at SMLT, Stacked VLANS, and of course
spanning tree designs - SMLT seems reasonable but
I want to know what other people's experience is.

I've got a half-dozen 8600s that serve about a hundred
workgroup switches, which serve a few thousand users.

 

[norteldude78]

You can use multiple spanning tree groups to utilize the unused links. It is complex and takes some planning...

peace

 

[Alainv]

Stacked vlan's is complex. The mac-address are still populating the fdb's.

Spanning tree. Then you have to look into RSTP/MSTP. But with nortel you have a better alternative with SMLT.

Be sure that you connect you servers away from the backbone.(unless you install them with teaming on 2 8600)
Use 55X0, it's less expensive then the userports on the 8600 chassis.
And the advantage is that you get better loadbalancing results.

 

[neilchapman]

Anthony,

Help me understand what is coming that will require you to carry those subnets to other places in the network?

Don't dump your L3 core just yet.

One of the great advantages of the 8600 platform is the RSMLT feature - Routed Switched Multi-Linked Trunks. It is wicked fast and very useful.

Neil