05-16-2007 05:19 AM - edited 03-05-2019 04:06 PM
Hello,
can any one tell me why do we configure
STP extended system-id on 3750 IOS switches, though we could set up priority with normal priority commands .
Please see the below details.
spanning-tree mode pvst
spanning-tree portfast bpduguard default
spanning-tree extend system-id
IOS 3750 switch# sh spanning-tree vlan 701
VLAN0701
Spanning tree enabled protocol ieee
Root ID Priority 33469
Address 0017.952b.9d00
This bridge is the root
Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec
Bridge ID Priority 33469 (priority 32768 sys-id-ext 701)
Address 0017.952b.9d00
Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec
Aging Time 14400
Please let me know what is Extended system ID in STP.
Thanks,
Akber.
05-16-2007 05:38 AM
Friend,
When the spanning tree extended system ID is used, the switch adds the VLAN number to the priority defined .i.e in your case the default priority + 701.
32768 + 701 = 33469
HTH, rate if it does
Narayan
05-16-2007 04:12 PM
hi,
When you use PVST and other advance mode,the Extented system id come into picture,because the BPDU now have to carry pirority and the VLAN that BPDU belong to and so Extented system id is used,in normal STP Vlan informtion is not required since only one instance is running.
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