From: Lou Ioanni (louisccie_r_s@yahoo.com)
Date: Tue Feb 20 2007 - 16:21:11 ART
Yes each vlan has its own root depending on the priority. If priorities are the same then it uses the mac to select the root. Each vlan and priorities are combined to create a unique ID. Check the floowing link for a siminlar question and answers:
http://www.velocityreviews.com/forums/t37177-bridge-priority-and-sysidext-number.html
Gobind <gobind@inbox.com> wrote: If the sys-id-ext usually correlates to Vlan Number,it means like for Vlan Number 1 the sys-id-ext would be 1,right? it is taken automatically or manually? I am confused about the part that the If in a switch every Vlan has its own priority then when the Root Election occurs,does it occurs to every Vlan,lets say there are 3 Vlans and what if it have different Priority then is it also possible that on Switch would be Root Bridge for 1 Vlan and not other two(due to higher Priority)?
-----Original Message-----
From: louisccie_r_s@yahoo.com
Sent: Tue, 20 Feb 2007 10:59:29 -0800 (PST)
To: gobind@inbox.com, ccielab@groupstudy.com
Subject: Re: Bridge Priority
I am not sure if you refering to a specific lab exercise, but in real environments you can select which switch you want to be the Root Bridge for specific vlans by lowering the priority from the default 32768. The lower the priority the more prefered to be the root (example 32000). If you want to FORCE a specific switch to be the root then you set priority 0. For example:
spanning-tree vlan 10-14 priority 0 (This will set this switch to be the root for vlans 10,11,12,13,14)
You can set a different root bridge for each group of vlans for load balancing. You can direct certain vlans traffic through one distribution switch and other vlans through the other distribution reduntant switch for load balancing L2 traffic.
Usually is good to set the L3 distribution switches as the Root bridges for the vlans attached to the access layer switches attached to it.
Thanks,
Loizos Y.
CCIE#10702 R & S
Gobind <gobind@inbox.com> wrote: Hi Guys,
I have some confusion wiht the Bridge Priority.In Some CBTs I am getting
to hear that:-
Bridge Priority is Default Priority(32768) - Vlan Number
I asked my friend,he said Default Priority is Default Priority + Vlan
Number
In one Cisco Dumentation it is written:-
"Each VLAN on each network device has a unique 64-bit bridge ID
consisting of a bridge priority value, an extended system ID, and an STP
MAC address allocation"
Source:- http://www.cisco.com/en/U
S/products/hw/switches/ps708/products_configuration_guide_chapter09186a008016
0a5b.html#wp1040218
I am really confused(maybe I am getting it wrong) what Priority(in STP
is),also I am not getting if the Priority is Default priority + Vlan
Number or - Vlan Number then what Vlan Number is it refering to? I mean
the Trunk belongs to every Vlan then which Vlan Number it takes while
making the election.(when it sends BPDU i.e.)
Gobind
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