[c-nsp] Migration to Rapid-PVST

[Per Carlson]

On Sat, May 13, 2006 at 02:50:27PM +0200, Robert Hass wrote:

>Basing on my first post with network diagram how many instances you
>recommend to have ? And which switches should be root-bridges for these
>instances.

The number of instances doesn't matter that much, a couple would
suffice. I would choose the switches connecting to the 7304's as
primary respective secondary root. It's the forwarding path
towards those switches that should be optimized. 

Are you doing any load-balancing on the 7304's, i.e. each 7304 is
the primary HSRP gateway for half of the Vlan's? If not, I would
purpose such a scheme. The easiest (to operate and maintain) way
is to allocate a large contigous Vlan range to each 7304. Like
Vlan 1-2047 to one 7304, and 2048-4094 to the other.  Put each of
the ranges into separate MST instances, and let the switch
connecting to the 7304 be primary root for one of the instances,
and secondary for the other.

>We have configured bpdu-filter and SPT portfast at customers ports.
>Most of customers using static routing, so We're terminating them on
>both our 7304 routers providing redundancy with HSRP.

That will make the STP converging quite fast. 

>Most of VLANs carring up to 2-6 MACs. I worst case it will be 50 VLANs
>* 6 MACs = 300 MACs.

That's a low number of MAC-addresses. No problem here either.

>>Be aware that there are two different MST implementations in IOS,
>>one pre-standard and one standard. As far as I have seen, those
>>will interoperate without any problems. But running the same type
>>in the whole network is probably a Good Thing (tm).
>
>I have 12.2(25)SED and 12.2(25)SEE on 3550/3560/3750 and 12.1(22)EA7 on
>2950. Is MST implementation in 12.1(22)EA7 is same that in
>12.2(25)SE{D/E} ?

Not sure, we don't have any 2950's in our network. If you dig up
the Config Guide for the newest IOS version and checks the "MST
Config Guide", you will find info about from which IOS version the
standardized MST is used.

-- 
Per Carlson, Sr. Network Developer