Administrator Guide

29 Dell Campus Networking Interoperability with Cisco Catalyst 1.1 | version 1.1
2.7 Multiple Spanning Tree Protocol
Multiple Spanning Tree Protocol (MSTP, 802.1Q-2005) defines an extension to RSTP by allowing VLANs to
be grouped together in MST instances. This reduces the number of STP instances found with PVSTP+
deployments, increasing available compute resources on switches participating in STP. Figure 10 shows how
the previous RPVSTP+ topology can be simplified into two MST instances. MST 1 handles VLANs 30-32 and
MST 2 handles VLANs 33-35 reducing the number of STP instances from six to two with each N-Series
switch being the root bridge for half of the configured VLANs. This can be useful if the maximum number of
RSTP instances available on a given switch are exceeded.
MST 1 and 2
MST 1
MST 2
Cisco 6504
Dell N3024-1 Dell N3024-2
(MST Root 1)
(MST Root 2)
Multiple Spanning Tree Protocol
Note: All switches participating in the MSTP topology must have the same name, revision and instance
mapping.