Bridge IDs

[shane.kearney]

Which of the following Bridge IDs would win the election.

32768:0200.1111.1111

32768:0200.2222.2222

200:0200.1111.1111

0200:0200.2222.2222

40,000:0200.1111.1111

[shane.kearney]

this question is from the icnd 2 book but i think the answer is wrong!!!

[Francois Tallet]

Assuming there is no trick like 0200 being octal vs 200 decimal;-) I would vote for 200:0200.1111.1111

Regards,

Francois

[shane.kearney]

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

[Giuseppe Larosa]

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

[shane.kearney]

Last Question,

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

Thanks for all the help.

[Giuseppe Larosa]

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

[Francois Tallet]

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