Virtual Private LAN Services
7750 SR OS Services Guide Page 381
Mode
To be compatible with the different iterations of the IEEE 802.1D standard, the 7750 SR supports
several variants of the Spanning Tree protocol:
•
rstp — Rapid Spanning Tree Protocol (RSTP) compliant with IEEE 802.1D-2004 -
default mode
•
dot1w — Compliant with IEEE 802.1w
•
comp-dot1w — Operation as in RSTP but backwards compatible with IEEE 802.1w
(this mode was introduced for interoperability with some MTU types)
•
mstp — Compliant with the Multiple Spanning Tree Protocol specified in IEEE 802.1Q
REV/D5.0-09/2005 . This mode of operation is only supported in an mVPLS.
See section Spanning Tree Operating Modes on page 335 for details on these modes.
CLI Syntax: config>service>vpls service-id# stp
mode {rstp | comp-dot1w | dot1w | mstp}
Default: rstp
Bridge Priority
The
bridge-priority command is used to populate the priority portion of the bridge ID field
within outbound BPDUs (the most significant 4 bits of the bridge ID). It is also used as part of the
decision process when determining the best BPDU between messages received and sent. When
running MSTP, this is the bridge priority used for the CIST.
All values will be truncated to multiples of 4096, conforming with IEEE 802.1t and 802.1D-2004.
CLI Syntax: config>service>vpls service-id# stp
priority bridge-priority
Range:
1 to 65535
Default: 32768
Restore Default: no priority
Max Age
The
max-age command indicates how many hops a BPDU can traverse the network starting from
the root bridge. The message age field in a BPDU transmitted by the root bridge is initialized to 0.
Each other bridge will take the message_age value from BPDUs received on their root port and
increment this value by 1. The message_age thus reflects the distance from the root bridge.
BPDUs with a message age exceeding max-age are ignored.
STP uses the max-age value configured in the root bridge. This value is propagated to the other
bridges via the BPDUs.
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