Am I wrong to think the bridge IDs can only be in multiples of 4096?

by the way you are correct and i was wrong

Hello Shane,

bridge IDs can only be in multiples of 4096 if using extended system-id otherwise they can be any value between 0 and 65535.

Hope to help

Giuseppe

Last Question,

How do you know if the extended System is used or not?

Thanks for all the help.

Hello Shane,

two ways

a) from configuration

b) do sh spanning-tree vlan 1

and

sh spanning-tree vlan x

if using extended id:

bridge priority in vlan x will be:

base pri + x

if not using extended id

bridge pri in vlan x = bridge pri in vlan 1

but MAC address differ

(the extended id feature is also called mac address reduction for this reason)

Hope to help

Giuseppe

Note that even with extended sysid, the priority will end up within the range 0-65535. Sure, you can only configure the higher 4 bits of the priority (by increment of 4096 indeed), but as you eventually add the vlan number to this configured priority, you end up with a figure that utilize the whole 64k range.

Regards,

Francois