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Catalyst 3550 Multilayer Switch Software Configuration Guide
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Chapter 17 Configuring MSTP
Configuring MSTP Features
•
Propagation—When an RSTP switch receives a TC message from another switch through a
designated or root port, it propagates the change to all of its nonedge, designated ports and to the
root port (excluding the port on which it is received). The switch starts the TC-while timer for all
such ports and flushes the information learned on them.
•
Protocol migration—For backward compatibility with 802.1D switches, RSTP selectively sends
802.1D configuration BPDUs and TCN BPDUs on a per-port basis.
When a port is initialized, the migrate-delay timer is started (specifies the minimum time during
which RSTP BPDUs are sent), and RSTP BPDUs are sent. While this timer is active, the switch
processes all BPDUs received on that port and ignores the protocol type.
If the switch receives an 802.1D BPDU after the port’s migration-delay timer has expired, it assumes
that it is connected to an 802.1D switch and starts using only 802.1D BPDUs. However, if the RSTP
switch is using 802.1D BPDUs on a port and receives an RSTP BPDU after the timer has expired,
it restarts the timer and starts using RSTP BPDUs on that port.
Configuring MSTP Features
These sections describe how to configure basic MSTP features:
•
Default MSTP Configuration, page 17-12
•
MSTP Configuration Guidelines, page 17-12
•
Specifying the MST Region Configuration and Enabling MSTP, page 17-13
(required)
•
Configuring the Root Switch, page 17-14
(optional)
•
Configuring a Secondary Root Switch, page 17-16
(optional)
•
Configuring the Port Priority, page 17-17
(optional)
•
Configuring the Path Cost, page 17-18
(optional)
•
Configuring the Switch Priority, page 17-19
(optional)
•
Configuring the Hello Time, page 17-19
(optional)
•
Configuring the Forwarding-Delay Time, page 17-20
(optional)
•
Configuring the Maximum-Aging Time, page 17-21
(optional)
•
Configuring the Maximum-Hop Count, page 17-21
(optional)
•
Specifying the Link Type to Ensure Rapid Transitions, page 17-22
(optional)
•
Restarting the Protocol Migration Process, page 17-22
(optional)