Kim Graham wrote:
Sorry for being so vague, it was first thing in the morning,
just getting my first cup of coffee and rubbing the sleep out
of my eyes. (Yes, I need a life if I wake up thinking about
these questions.)
This is a 6513.
That is what I thought. The BID is the MAC address on the
card, hence why I am curious as to how this has come about. :)
Here is the header output of the show spantree command, the
second 6513 shows spanning tree as disabled:
VLAN 1
Spanning tree mode PVST+
Spanning tree type ieee
Spanning tree enabled
Designated Root 00-00-00-00-00-00
Designated Root Priority0
Designated Root Cost0
Designated Root Port1/0
Root Max Age 0 sec Hello Time 0 sec Forward Delay 0 sec
Bridge ID MAC ADDR 00-00-00-00-00-00
Bridge ID Priority 32769 (bridge priority: 32768, sys
ID ext: 1)
Bridge Max Age 20 sec Hello Time 2 sec Forward Delay 15 sec
All the ports show as VLAN1.
--
As my curiosity grew I checked Per-VLAN.
Our closests are configured to look at one of the core switches
as the root bridge, the other core as the secondary root
bridge. I went to one of the closets and received the same
output as above for show spantree.
But if I issue show spantree I receive the information
that shows me which device it uses as the root bridge.
Would it be safe to say then that due to PVST+ the MAC address
comes out as all zero's when you issue show spantree without
a VLAN designation?
I guess so. Thanks for discovering this for us. It's pretty strange, but on
the other hand it sort of makes sense. When you do PVST, the MAC address is
different for each VLAN. If you don't specify a VLAN, the output doesn't
know what to say, I guess.
Kim
From: Priscilla Oppenheimer
Date: 2002/07/11 Thu PM 03:20:41 EDT
To: [EMAIL PROTECTED]
Subject: RE: All 0's MAC Root Bridge [7:48578]
Kim Graham wrote:
The other day I was delving a bit into spanning tree and I
came
across something that puzzled me.
Searching out which device was the root bridge I found the
MAC
address (BID) on the root bridge to be all zero's. (show
spantree snippets).
Spanning tree mode PVST+
Spanning tree type ieee
Designated Root 00-00-00-00-00-00
Bridge ID MAC ADDR 00-00-00-00-00-00
Without finishing chapter 7 (Spanning Tree) in my LAN
switching
book I am puzzled as to whether this is a preset MAC
address or
self assigned.
The Bridge ID MAC address is preassigned to the switch by the
manufacturer.
The address would be one of the many assigned to the
supervisor or backplane
in Cisco's case, depending on the switch model. Which model
are you using?
Seeing all zeroes is extremely strange, as you know, since
you're asking
this question! ;-)
A few things I'm wondering about:
What state was the spanning tree in? Was it still converging?
Did the outpu
continue to say this weirness, or did it change after a while?
For which VLAN were you displaying this information? I notice
that you're
doing Per-VLAN Spanning Tree. Could this info be for a VLAN
that doesn't
actually exist or for a VLAN where spanning tree is disabled?
Can you send
us your config?
I guess the bottom line is that we need more info from you.
Priscilla
Any thoughts? Why or how did this occur?
Kim
Message Posted at:
http://www.groupstudy.com/form/read.php?f=7i=48705t=48578
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