Multiple Instance Spanning-Tree Operation

Configuring MSTP

Syntax: spanning-tree forward-delay

Sets time the switch waits between transitioning from listening to learning and from learning to forwarding states.

(Range: 4 - 30; Default: 15.)

Syntax: spanning-tree legacy-mode

Sets spanning-tree protocol to operate in 802.1D legacy mode (STP-compatible).

(Default: MSTP-operation.)

The no form of the command returns the switch to the default 802.1s native mode (MSTP-operation).

Syntax: spanning-tree legacy-path-cost

Sets spanning-tree to operate with 802.1d (legacy) path cost values.

(Default: 802.1t.)

The no form of the command returns the switch to the default 802.1t (not legacy) path cost values.

Syntax: spanning-tree hello-time < 1..10 >

If MSTP is running and the switch is operating as the CIST root for your network, this command specifies the time in seconds between transmissions of BPDUs for all ports on the switch configured with the Global option. (the default). This parameter applies in MSTP, RSTP and STP modes. During MSTP operation, you can override this global setting on a per- port basis with this command: spanning-tree < port-list> hello- time < 1..10 > (see page 4-27). (Default: 2.)

Syntax: spanning-tree max-hops < hop-count>

This command resets the number of hops allowed for BPDUs in an MST region. When an MSTP switch receives a BPDU, it decrements the hop-count setting the BPDU carries. If the hop- count reaches zero, the receiving switch drops the BPDU. Note that the switch does not change the message-age and maximum-age data carried in the BPDU as it moves through the MST region and is propagated to other regions. (Range: 1 - 40; Default: 20)

Syntax: spanning-tree maximum age

Sets the maximum age of received STP information before it is discarded.

(Default: 20.)

4-23