12-12
Catalyst 2950 Desktop Switch Software Configuration Guide
78-14982-01
Chapter 12 Configuring RSTP and MSTP
Configuring RSTP and MSTP Featur es

Default RSTP and MSTP Configuration

Table 12-3 shows the de fault RST P and M STP configur ation .

RSTP and MSTP Configuration Guidelines

These are th e configurat ion g uidelin es for RSTP an d MST P:
•The UplinkFast, BackboneFast, and cross-stack UplinkFast features are not supported with the
RSTP and MSTP.
•Per-VLAN RST P is not supp ort ed. When yo u e nabl e M ST by using the spanning-tree mode mst
global configurati on comm and, RST P is enable d.
•PVST, PVST+ and MSTP are supported, but only one version can be active at any time; all VLANs
run PVST, or all VLANs run MSTP.
•VTP propagation of the MST configuration is not supported. Ho wever, you can manually configure
the MS T configur ati on (r egio n nam e , revision num ber, and VL AN-t o-in stanc e map ping) o n e ach
switch within the MST region by using the command-line interface (CLI) or through the SNMP
support.
•For load b ala nci ng ac ro ss r edund an t pa ths i n t he n etwor k to work, a ll V LAN -to- inst ance mapping
assignme nts must mat ch; other wise, all tra ffic flows on a single link.
•All MST b ounda ry port s m ust b e fo rwa rding for lo ad b ala ncing be twee n a PVST + a nd an M ST
cloud. For this to happen, the IST master of the MST cloud should also be the root of the CST. If
the MST cloud consists of multiple MST regions, one of the MST regions must contain the CST root,
and al l of t he o th er M ST r egions mu st have a bette r p ath t o th e roo t con tai ned w it h the M ST c lou d
than a path thr oug h the PVST + c loud. You might h ave to manual ly con figure the swit che s in the
clouds.
•Partitionin g the ne twork into a large num ber of regions i s not recom mende d. However, if this
situation is unavoidable, we recommend that you partition the switched LAN into smaller LANs
interco nnected by rout ers or non-La yer 2 devices.
Table 12-3 Default RSTP and MSTP Configuration
Feature Default Setting
Spanning-tree mode PVST (MSTP and RST P are disabled).
Switch p rior ity (con figurable on a p er-CIST inte rface basi s) 32768.
Spanni ng-t ree port pr iorit y (c on figurable on a p er-CIST int erfac e ba sis) 128.
Spanni ng-tree por t cost (configurab le on a per-CIST inter face basis) 1000 Mbps: 4.
100 Mb ps: 19.
10 Mbps: 100.
Hello time 2 seconds.
Forward-de lay time 15 second s.
Maximu m- ag ing t im e 20 sec onds.
Maximu m hop coun t 20 hops.