Specifications

CHAPTER 3
Spanning Tree
(config-mst)# revision number
(config-mst)# instance number vlan vlan_range
(config-mst)# end
# show spanning-tree mst
To be compatible with 802.1Q trunking, which has one common Spanning Tree (CST) for all VLANs, MST runs one
instance of an Internal Spanning Tree (IST). The IST appears as one bridge to a CST area and is MST instance number 0.
The original MST Spanning Trees (called M-Trees) are active only in the region; they combine at the edge of the CST
area to form one.
Spanning Tree Stability Mechanisms
Spanning Tree has several additional tools for tuning STP to protect the network and keep it operating properly. They
include:
n PortFast (discussed previously)
n UplinkFast
n BackboneFast
n BPDU Guard
n BPDU Filtering
n Root Guard
n UDLD
n Loop Guard
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CCNP SWITCH 642-813 Quick Reference by Denise Donohue
9781587140112.qxd 11/23/09 11:35 AM Page 41
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