[c-nsp] Maximum spannig tree instances

[Geoffrey Pendery]

Yes, but he also mentions MST, which has a much more restrictive limit.
As far as I've seen, 802.1s itself only allows 64 instances (see
http://en.wikipedia.org/wiki/Spanning_tree_protocol , or search for
the proper RFC docs)
But all the Cisco docs I've found this morning say they only support 16:
for example:
http://www.cisco.com/en/US/docs/switches/lan/catalyst6500/ios/12.2SXF/native/configuration/guide/spantree.html#wp1064097

I could have sworn I found stuff saying that our gear would support 64
of them, and we've been contemplating more than 40 in recent designs,
but I guess I'll have to validate in the lab whether it's actually 16
or 64 for our chassis and code.

So keep in mind that if you're moving from RPVST to MST, you're
talking about fewer instances, by necessity.


-Geoff


On Tue, Jul 14, 2009 at 3:45 AM, <A.L.M.Buxey at lboro.ac.uk> wrote:
> Hi,
>
>> ... but it doesn't say anything about the number of STP instances.
>
> things go wonky when you have more than 1800 virtualports per slot
> (which you didnt quite reach) (1200 on older eg 100mbit blades)
> with 13,000 in total (PVST+), 10,000 in total (RPVST+)
>
> however, with MST, you can have 6000 virtual ports per blade and 50,000
> in total (yay!)
>
> however, this is all about logical interfaces. you want to know the
> STP instance?
>
> regarding maximum STP instances... I believe theres a platform limit
> of 1024 because of the MAC to VLAN bridge mapping on the platform -
> but, from the values above, you can see that virtual ports would
> hit you quite quickly without appropriate control of the VLANs
>
> alan
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