About Mst-To-Pvst+ Interoperability (Pvst+ Simulation) - Cisco Catalyst 4500 Series Software Configuration Manual

Chapter 23 Configuring STP and MST
Bridge ID
Interface
---------------- ---- --- --------- -------- --------------------------------
Fa4/4
Fa4/5
Switch# show spanning-tree summary
Root bridge for:MST01
EtherChannel misconfiguration guard is enabled
Extended system ID
Portfast
PortFast BPDU Guard
Portfast BPDU Filter is disabled by default
Loopguard
UplinkFast
BackboneFast
Pathcost method used is long
Name
---------------------- -------- --------- -------- ---------- ----------
MST00
MST01
---------------------- -------- --------- -------- ---------- ----------
2 msts
Switch#

About MST-to-PVST+ Interoperability (PVST+ Simulation)

The PVST+ simulation feature enables seamless interoperability between MST and Rapid PVST+. You
can enable or disable this per port, or globally. PVST+ simulation is enabled by default.
However, you may want to control the connection between MST and Rapid PVST+ to protect against
accidentally connecting an MST-enabled port to a Rapid PVST+-enabled port. Because Rapid PVST+ is
the default STP mode, you may encounter many Rapid PVST+-enabled connections.
Disabling this feature causes the switch to stop the MST region from interacting with PVST+ regions.
The MST-enabled port moves to a PVST peer inconsistent (blocking) state once it detects it is connected
to a Rapid PVST+-enabled port. This port remains in the inconsistent state until the port stops receiving
Shared Spanning Tree Protocol (SSTP) BPDUs, and then the port resumes the normal STP transition
process.
You can for instance, disable PVST+ simulation, to prevent an incorrectly configured switch from
connecting to a network where the STP mode is not MSTP (the default mode is PVST+).
Observe these guidelines when you configure MST switches (in the same region) to interact with PVST+
switches:
•
Priority 32769
Address 00d0.00b8.1400
Hello Time 2 sec
Role Sts Cost
Back BLK 1000
Desg FWD 200000
is enabled
is disabled by default
is disabled by default
is disabled by default
is disabled
is disabled
Blocking Listening Learning Forwarding STP Active
1
1
2
Configure the root for all VLANs inside the MST region as shown in this example:
Switch# show spanning-tree mst interface gigabitethernet 1/1
GigabitEthernet1/1 of MST00 is root forwarding
Edge port: no
Link type: point-to-point (auto)
Boundary : boundary
Bpdus sent 10, received 310
Catalyst 4500 Series Switch, Cisco IOS Software Configuration Guide - Cisco IOS XE 3.9.xE and IOS 15.2(5)Ex
About MST-to-PVST+ Interoperability (PVST+ Simulation)
(priority 32768 sys-id-ext 1)
Max Age 20 sec Forward Delay 15 sec
Prio.Nbr Status
240.196 P2p
128.197 P2p
0 0
0 0
0 0
(trunk) port guard : none
bpdu filter: disable
(PVST) bpdu guard : disable
2 3
2 3
4 6
(default)
(default)
(default)
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