From: Katson Yeung (kyeung@xxxxxxxxxxxxxx)
Date: Thu Jun 20 2002 - 11:49:39 GMT-3
Just did a small test to see how bridge priority 0 and 1 struggle between
a Catalyst and a bridged interface in a router.
<!- initially, the Cat switch is the root bridge with priotity 32768 ->
R6#sh spanning
Bridge group 1 is executing the IEEE compatible Spanning Tree protocol
Bridge Identifier has priority 32768, address 00e0.1ebb.6335
Configured hello time 2, max age 20, forward delay 15
Current root has priority 32768, address 0003.9f63.3013
Root port is 9 (Ethernet1), cost of root path is 100
Port Number size is 9
Topology change flag not set, detected flag not set
Times: hold 1, topology change 35, notification 2
hello 2, max age 20, forward delay 15
Timers: hello 0, topology change 0, notification 0
bridge aging time 300
<!- then I configure the router's bridge 1 to priority 1 ->
R6(config)#bridge 1 priority 1
R6#sh spanning
Bridge group 1 is executing the IEEE compatible Spanning Tree protocol
Bridge Identifier has priority 1, address 00e0.1ebb.6335
Configured hello time 2, max age 20, forward delay 15
We are the root of the spanning tree
Port Number size is 9
Topology change flag set, detected flag set
Times: hold 1, topology change 35, notification 2
hello 2, max age 20, forward delay 15
Timers: hello 1, topology change 32, notification 0
bridge aging time 15
<!- Then I change the Catalyst's bridge to priority 0 -!>
Console> en
Console> (enable) set spantree priority 0 40
Spantree 40 bridge priority set to 0.
Console> (enable)
Console#6
[Resuming connection 6 to r6 ... ]
R6#sh spanning
Bridge group 1 is executing the IEEE compatible Spanning Tree protocol
Bridge Identifier has priority 1, address 00e0.1ebb.6335
Configured hello time 2, max age 20, forward delay 15
Current root has priority 0, address 0003.9f63.3027
Root port is 11 (Ethernet3), cost of root path is 100
Port Number size is 9
Topology change flag set, detected flag not set
Times: hold 1, topology change 35, notification 2
hello 2, max age 20, forward delay 15
Timers: hello 0, topology change 0, notification 0
bridge aging time 15
---------------------------------------------------------------------
You can see. Bridge priority 0 wins over bridge priority 1. And 0 is an
acceptable value. It does not mean 0 = disabled, or not involved in
root-bridge election.
On Thu, 20 Jun 2002 FZahrt@NECBNS.com wrote:
> Peter,
> That is odd. I might be overstepping my knowledge level here, but I
> thought if you set spantree to a priority of 0, then it could not become the
> root bridge. A setting of 1 is the lowest I thought you could do for root
> election, hence it would have the highest priority. If I am off base on
> this, please correct me.
>
>
>
> Frank Zahrt III
> CCDP, CCNP Voice Specialist, CCSE, FSCE
> NEC Senior Network Engineer
>
>
> -----Original Message-----
> From: peter brown [mailto:pita40@hotmail.com]
> Sent: Thursday, June 20, 2002 9:17 AM
> To: ccielab@groupstudy.com
> Cc: chrishugo@yahoo.com
> Subject:
>
> I am still having a problem answering this question about stp. If you want
> to make a say vlan 10 to use the switch as a the root bridge. which of this
>
> statement is correct.
>
> set spantree priority 1 10
>
> set spantree priority 0 10
>
> I you donot want to use set spantree root command.
>
> Help.
> I did it with 2 cat 4000s and the switch with "set spantree priority 0 10"
> command always wins, but I keep seeing documents that uses priority 1.
> Example in Fatkid and even the link form cisco. Which one is correct for
> cisco sake.
>
>
>
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