[c-nsp] Maximum spannig tree instances

[Jon Lewis]

On Tue, 14 Jul 2009, Gert Doering wrote:

> On Tue, Jul 14, 2009 at 09:26:13AM -0400, Jon Lewis wrote:
>> But isn't that the whole point of MST?
>
> We have found MST to be mostly pointless...
>
> "Too much hassle, too little gain"

So do you just do rapid-pvst and limit which VLANs are allowed on all 
trunk ports?  I know you're not a fan of VTP, and I suppose this may be 
another reason.  Even with the trunks limiting which VLANs get through, 
VTP still creates all the vlans on all the switches, and in a PVST setup, 
they run a spanning tree instance for each VLAN, even if they aren't 
really participating in the VLAN.

> two VLANs that share the same topology - which maps very poorly to MST
> instances.  At the same time, there is a fairly high dynamic in adding
> and removing VLANs, which is *quite* painful with MST instance
> mappings...

I've wondered about that...if we were to move to MST, we're going to have 
to assign every VLAN to an MST instance, which could get messy.

Maybe it is time to just turn off VTP and manually create VLANs only where 
they're needed, in which case we'll only have to worry about the number of 
PVST instances on the central 6509s, as there's no way we'd run up to 128 
VLANs on a 3550.  We've actually never done VTP on the 6500s...only on the 
3550s.  I figured if VTP ever did blow up, I didn't want it blowing on the 
central switches...just the edges.


----------------------------------------------------------------------
  Jon Lewis                   |  I route
  Senior Network Engineer     |  therefore you are
  Atlantic Net                |
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