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RSTP Topology change, MSTP no

Hp 5300 Went Down
Occasional Advisor

RSTP Topology change, MSTP no

Hi,i have a network of 60 switches.

35 running rstp, the rest running MSTP.

I have a look in stp with "show spanning-tree" command and i have a strange result.

All 35 switches running RSTP recalculate the topology very often, but switches with MSTP doesn't recalculate it since 150 days.

All switches have the same VLANS.

We not report any disconnection or instability
3 REPLIES

Re: RSTP Topology change, MSTP no

Sorry do not have a solution but we reported the same problem on our network.

We eventually changed all our switches to RSTP, though I know that is a backward step especially as we have a lot of VLANs.

I'd like to move forward to MSTP but are unsure that the network will "just sort itself out", if we switch MSTP on on all the switches...
Pieter 't Hart
Honored Contributor

Re: RSTP Topology change, MSTP no

Look into rules designating the spanning-tree "root".
You basically got two spnannig-tree domains wich are connected.

I think you'll find MSTP switches have their own MSTP root and see no real topology change.
While the RSTP switches may go through the whole topology-change sequence every time some random port (or specific ports from a single wrong configured switch!) goes up/down.

You may find some improvement in designating the right switch as RSTP-root using the stp-priority.


maybe this document helps
http://www.cisco.com/en/US/docs/switches/lan/catalyst3550/software/release/12.1_13_ea1/configuration/guide/swmstp.pdf

see the section about "boundary ports":
A boundary port is a port that connects an MST region to a single spanning-tree region running RSTP, or to a single spanning-tree region running 802.1
Pieter 't Hart
Honored Contributor