Is "spanning-tree vlan priority 0" valid?

[gwhuang5398]

3560 command reference says valid priority values are 4096, 8192, ... however I tried "spanning-tree vlan priority 0" and the command was accepted. When I "show spanning-tree brief", the vlan I configured did show priority 0.

Did I read the command reference right? (I looked at 12.2(44) and 12.2(52)

Is "priority 0" a valid configuration even if IOS accepts it?

Thanks

[jonatrod · Accepted solution]

Good morning gwhuang5398

My name is Johnnatan and I am part of the Small business Support community.  This is a valid value for this command, actually has more priority than 4096. The priority order starts from 0 and then increases in 4096.

     0, 4096, 8192, 12288, …

If you configure two switches one of them with priority ¨0¨ and the other one with priority  ¨4096¨, the first one with priority ¨0¨ is going to be the root.

I hope you find this answer useful, if it was satisfactory  for you, please mark the question as Answered.

Thank you.

Johnnatan Rodriguez Miranda.

Cisco Network Support Engineer.

[pagamar2004]

Hi Jonatrod,

when two switches are set with "priority 0" the first, and "root primary" the second,

which will become root-bridge? Some say the second, most say the first.

IMHO, if I'm not wrong, the second Switch generates a Syslog complaining it can't

grant to become root-bridge, because of the presence in the network of the

"priority 0" Switch (it cannot set himself 4096 below).

So I think the two switches will set both to "priority 0", and tie break on their MAC...

The lowest MAC generates a lowest BID, and this will decide the root-bridge. Isn't it?