Cisco 7609 User Manual

15-40
Cisco 7600 Series Router Cisco IOS Software Configuration Guide—12.1E
78-14064-04
Chapter 15 Configuring STP and IEEE 802.1s MST
Configuring IEEE 802.1s MST
Configuring MST Instance Port Parameters
To configure MST instance port parameters, perform these tasks:
This example shows how to configure MST instance port parameters:
Router(config)# interface fastEthernet 4/4
Router(config-if)# spanning-tree mst 1 ?
cost Change the interface spanning tree path cost for an instance
port-priority Change the spanning tree port priority for an instance
Router(config-if)# spanning-tree mst 1 cost 1234567
Router(config-if)# spanning-tree mst 1 port-priority 240
Router(config-if)# ^Z
Router# show spanning-tree mst 1 interface fastEthernet 4/4
FastEthernet4/4 of MST01 is backup blocking
Edge port:no (default) port guard :none (default)
Link type:point-to-point (auto) bpdu filter:disable (default)
Boundary :internal bpdu guard :disable (default)
Bpdus (MRecords) sent 125, received 1782
Instance Role Sts Cost Prio.Nbr Vlans mapped
-------- ---- --- --------- -------- -------------------------------
1 Back BLK 1234567 240.196 1-10
Router#
Restarting Protocol Migration
A switch running both MSTP and RSTP supports a built-in protocol migration mechanism that enables
the switch to interoperate with legacy 802.1D switches. If this switch receives a legacy 802.1D
configuration BPDU (a BPDU with the protocol version set to 0), it sends only 802.1D BPDUs on that
port. An MSTP switch can also detect that a port is at the boundary of a region when it receives a legacy
BPDU, an MST BPDU (version 3) associated with a different region, or an RST BPDU (version 2).
However, the switch does not automatically revert to the MSTP mode if it no longer receives 802.1D
BPDUs because it cannot determine whether the legacy switch has been removed from the link unless
the legacy switch is the designated switch. A switch also might continue to assign a boundary role to a
port when the switch to which it is connected has joined the region.
Command Purpose
Step 1
Router(config-if)# spanning-tree mst x cost y
Configures the MST instance port cost.
Step 2
Router(config-if)# spanning-tree mst x
port-priority y
Configures the MST instance port priority.
Step 3
Router# show spanning-tree mst x interface y
Verifies the configuration.

Cisco 7609 Specifications

General

Chassis Slots	9
Switch Fabric Capacity	720 Gbps
Power Supply Options	AC or DC
Product Type	Router
Form Factor	Rack-mountable
Supported Line Cards	Various Cisco 7600 Series line cards
Operating System	Cisco IOS
Management	CLI, SNMP
Forwarding Performance	400 Mpps
Maximum Power Consumption	4000 Watts
Redundancy	Yes
Interfaces/Ports	Various, depending on line cards installed