14.
Multiple Spanning Tree Protocol (MSTP)
MN700004 Rev 01
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Prerequisites
The MSTP implementation operates over MSTIs which are, in turn, mapped into groups of
VLANs. However, since the MSTP does not enforce VLAN membership state for ports, a
situation of inconsistency between the MSTP port’s state and the real state of the port may
arise. For example, MSTP may set a port state on MSTI3 to be forwarding, when the instance
is mapped to VLANs 3-5. If the port is not a member of VLAN 4, it will effectively be
blocked on that VLAN, although the MSTP will show a forwarding state.
Make sure that this consistency is maintained, either by matching the VLAN memberships to
the MSTP state or by changing MSTP parameters (such as path-cost and priority) so the
traffic will be diverted to correct ports.
Default MSTP Configuration
Table 14-2 lists the MSTP default parameter values.
Table 14-2 MSTP Default Parameter Values
P a r a m e t e r D e f a u l t
V a l u e
Multiple Spanning tree mode (MSTP)
Disabled
Spanning tree port priority
128
Hello time
2 seconds
Forward delay time
15 seconds
Maximum aging time
20 seconds
Maximum hop count
40 hops
Revision number
1
Default MTS Instance
0
Bridge priority
32768
Path cost
See table 14-3