Configure Spanningtree portfast on a trunk :

S3750(config-if)#spanning-tree portfast trunk
%Warning: portfast should only be enabled on ports connected to a single
host. Connecting hubs, concentrators, switches, bridges, etc… to this
interface when portfast is enabled, can cause temporary bridging loops.
Use with CAUTION

Some other spannings-tree features.

S3750(config-if)#spanning-tree ?
bpdufilter Don’t send or receive BPDUs on this interface
bpduguard Don’t accept BPDUs on this interface

More information :

To set the Switch as root for Spanning-tree :

S3750(config)#spanning-tree vlan 5 priority 4000
% Bridge Priority must be in increments of 4096.
% Allowed values are:
0 4096 8192 12288 16384 20480 24576 28672
32768 36864 40960 45056 49152 53248 57344 61440
The lower the value, the higher the change the switch will be root.

S3750#sh span vlan 5

Spanning tree enabled protocol ieee
Root ID Priority 8197
Address 0013.c494.ac80
This bridge is the root
Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec

Bridge ID Priority 8197 (priority 8192 sys-id-ext 5)
Address 0013.c494.ac80
Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec
Aging Time 300 sec

Interface Role Sts Cost Prio.Nbr Type
——————- —- — ——— ——– ——————————–
Po2 Desg FWD 12 128.496 P2p

About Joost van der Made


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