Multiple Instance Spanning-Tree Operation

802.1s Multiple Spanning Tree Protocol (MSTP)

Syntax: [no] spanning-tree < port-list> mcheck

Forces a port to send RSTP BPDUs for 3 seconds. This allows for another switch connected to the port and running RSTP to establish its connection quickly and for identifying switches running 802.1D STP. If the whole- switch force-version parameter is set to stp-compatible, the switch ignores the mcheck setting and sends 802.1D STP BPDUs out all ports. Disable this feature on all ports that are known to be connected to devices that are running 802.1D STP.

The no spanning-tree < port-list> mcheck command disables mcheck.

(Default: Yes – mcheck is enabled)

Syntax: spanning-tree < port-list> hello-time < global 1 - 10 >

When the switch is the CIST root, this parameter specifies the interval (in seconds) between periodic BPDU transmissions by the designated ports. This interval also applies to all ports in all switches downstream from each port in the < port-list>. A setting of global indicates that the ports in < port-list> on the CIST root are using the value set by the global spanning-tree hello-timevalue (page 5-24). When a given switch “X” is not the CIST root, the per-port hello-timefor all active ports on switch “X” is propagated from the CIST root, and is the same as the hello-timein use on the CIST root port in the currently active path from switch “X” to the CIST root. (That is, when switch “X” is not the CIST root, then the upstream CIST root’s port hello- time setting overrides the hello-timesetting configured on switch “X”).

(Default Per-Port setting: Use Global. Default Global Hello-Time: 2.)

Syntax: spanning-tree < port-list> path-cost < auto 1..200000000 >

Assigns an individual port cost that the switch uses to determine which ports are forwarding ports in a given spanning tree. In the default configuration ( auto ) the switch determines a port’s path cost by the port’s type:

10 Mbps: 2000000

100 Mbps: 200000

1 Gbps: 20000

Refer to “Note on Path Cost” on page 5-5for information on compatibility with devices running 802.1D STP for the path cost values

(Default: Auto).

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