Re: Bridge Priority

From: Gobind (gobind@inbox.com)
Date: Tue Feb 20 2007 - 16:10:52 ART


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_configurat
    ion_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

    __________________________________________________
    _____________________
    Subscription information may be found at:
    http://www.groupstudy.com/list/CCIELab.html

  --------------------------------------------------------------------

  It's here! Your new message!
  Get new email alerts with the free Yahoo! Toolbar.



This archive was generated by hypermail 2.1.4 : Thu Mar 01 2007 - 07:38:47 ART