mst spanning tree problem

philip_john · ‎05-23-2009

after adding mst on my n/w in dist which also contain hsrp & ospf, the n/w becomes very slow and as i add pvst, it becomes fast whearas in other building it works fine. this is new building and its topology is same as other building. plz suggests me and also tell me what is diff b/w mst & hsrp in stp prospective

christophhall · ‎05-23-2009

Are you doing PVST or MST as they are not the same - or maybe you are saying that when you switch back to pvst the problem goes away ?

Giuseppe Larosa · ‎05-24-2009

Hello Philip,

if the network includes other switches the type of STP has a direct effect on the capability to build a correct Spanning Tree.

In other words if there are other devices in addition to distribution switches you need to verify the STP mode running on them.

If they are running PVST you have two choices:

use PVST also on distribution switches with commands to make them the primary and secondary root bridges for all vlans/STP instances.

2) you need to migrate all switches to MST.

be also aware that to be in the same MST region the following must match:

MST region name

MST revision number

mappings of all possible vlans 1-4094 to MST instances.

if any of these don't match two switches consider each other as being part of different MST regions and can run only a single instance STP between them.

Hope to help

Giuseppe

philip_john · ‎07-18-2009

thanks for reply

actually i have not configured mst on access switches wheras it was configured on dist sw. Your reply to my ques solved my problem

Giuseppe Larosa · ‎07-19-2009

Hello Philip,

and so what you have done?

all devices are in PVST+

or all devices are now in same MST region?

Hope to help

Giuseppe