Configuring PVSTAG or PVRSTAG
This section describes the procedures for configuring PVSTAG:
The procedures for configuring PVRSTAG are identical.
This section does not describe how to configure data switching. Refer to the Implementing Multipoint Layer
2 Services module for more information.
Note
Enabling PVSTAG
PVSTAG is enabled for a particular VLAN, on a physical interface, by explicit configuration of that physical
interface and VLAN for PVSTAG.
Configuring PVSTAG parameters
The configurable PVSTAG parameters for each interface on each VLAN are:
• Root Priority and ID
• Root cost
• Bridge Priority and ID
• Port priority and ID
• Max Age
• Hello Time
For correct operation, these guidelines must be followed when configuring PVSTAG.
• Both gateway devices should be configured with a root bridge priority and ID that is better (lower) than
the bridge priority and Bridge ID of any device in the access network. It is recommended that you set
the root bridge priority and ID to 0 on the gateway devices.
• Both gateway devices should be configured with a root cost of 0.
• One gateway device should be configured with the bridge priority and ID that is higher than the root
bridge priority and ID, but lower than the bridge priority and ID of any other device in the network
(including the other gateway device). It is recommended that you set the bridge priority to 0.
• The second gateway device should be configured with a bridge priority and ID that is higher than the
root bridge priority and ID and the first gateway device bridge priority and ID, but lower than the bridge
priority and ID of any device in the access network. It is recommended that you set the bridge priority
to 1 for PVSTAG or 4096 for PVRSTAG. (For PVRSTAG, this is the lowest allowable value greater
than 0.)
• All access devices must be configured with a higher bridge priority than the gateway devices. It is
recommended that you use values of 2 or higher for PVSTAG, or 8192 or higher for PVRSTAG.
• For each spanning tree instance, the port path cost and other parameters may be configured on the access
devices, so as to ensure the desired port is placed into the blocked state when all links are up.
L2VPN and Ethernet Services Configuration Guide for Cisco ASR 9000 Series Routers, IOS XR Release 6.3.x
442
Implementing Multiple Spanning Tree Protocol
Configuring PVSTAG or PVRSTAG
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