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Catalyst 6500 Series Switch Software Configuration Guide—Release 8.7
OL-8978-04
Chapter 7 Configuring Spanning Tree
Configuring MISTP-PVST+ or MISTP on the Switch
Port Inst Port-State Cost Prio Portfast Channel_id
------------------------ ---- ------------- --------- ---- -------- ----------
1/1 1 forwarding 20000 32 disabled 0
3/1 1 forwarding 200000 32 disabled 0
3/25 1 forwarding 200000 32 disabled 0
3/26 1 forwarding 200000 32 disabled 0
3/27 1 forwarding 200000 32 disabled 0
3/28 1 forwarding 200000 32 disabled 0
3/29 1 forwarding 200000 32 disabled 0
3/30 1 forwarding 200000 32 disabled 0
7/1-4 1 blocking 5000 32 disabled 833
7/5 1 forwarding 20000 32 disabled 0
7/6 1 forwarding 20000 32 disabled 0
8/37 1 blocking 200000 32 disabled 0
8/38 1 blocking 200000 32 disabled 0
15/1 1 forwarding 20000 32 enabled 0
16/1 1 forwarding 20000 32 enabled 0
Console> (enable)
Configuring the MISTP Port Instance Cost
You can configure the port instance cost for an instance of MISTP or MISTP-PVST+. Ports with a lower
instance cost are more likely to be chosen to forward frames. You should assign lower numbers to ports
that are attached to faster media (such as full duplex) and higher numbers to ports that are attached to
slower media. The default cost differs for different media. The possible value for port instance cost is
1–268435456.
To configure the port instance cost for a port, perform this task in privileged mode:
This example shows how to configure the MISTP port instance cost on a port:
Console> (enable)
set spantree portinstancecost 1/1 cost 110110 2
Port 1/1 instances 1,3-16 have path cost 20000.
Port 1/1 instances 2 have path cost 110110.
This parameter applies to trunking ports only.
Console> (enable)
Configuring the MISTP Port Instance Priority
You can set the port priority for an instance of MISTP. The port with the lowest priority value for a
specific MISTP instance forwards frames for that instance. The possible port instance range is 0–63. The
possible port priority value is a multiple of 16 from 0–240. If all ports have the same priority value for
an MISTP instance, the port with the lowest port number forwards frames for that instance.
To configure the port instance priority on an MISTP instance, perform this task in privileged mode:
Task
Command
Configure the MISTP port instance cost on
a port.
set spantree portinstancecost
{
mod/port
}
[
cost
cost
]
[
instances
]
Task
Command
Configure the port instance priority on an MISTP
instance.
set spantree portinstancepri
{
mod/port
}
priority
[
instances
]
