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 Priority 0 > Designated Root Cost 0 > Designated Root Port 1/0 > 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=7&i=48705&t=48578 -------------------------------------------------- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
