[c-nsp] STP root switch election MAC address

[Amol Sapkal]

Thanks for the inputs Clinton.

I tried these commands on my 6500's and a couple of these don't work. The
'sh catalyst6000' command is available in the new IOS but not with the old
CatOS.


Best,
Amol



On 8/4/06, Clinton Work <clinton at scripty.com> wrote:
>
>
> The chassis or supervisor (depends upon platform) will have a range of
> reserved MACs assigned to it. MACs will be taken from the reserved range
> to
> use as the STP bridge ID.
>
> How the MACs are assigned depends if extended system ID (MAC reduction) is
> enabled or not. If extended system ID is enabled, one MAC or Bridge ID
> will
> be used for all STP instances (aka VLANs). If extended system ID is
> disabled
> then a unique MAC will be used for each STP instance (aka VLAN). Some
> switches don't allow you to disable extended system ID (ex 2950).
>
> 7609# show spanning-tree summary  | inc Ext
> Extended system ID           is enabled
>
> The exec command to look at the reserved MAC range varies by platform:
>
> 7609# show catalyst6000 chassis-mac-addresses
>   chassis MAC addresses: 64 addresses from 0011.20d8.7700 to
> 0011.20d8.773f
>
> 4500# show idprom chassis  | inc MAC
> MAC Base = 000d.65ab.aac0
> MAC Count = 64
>
> You can always check each STP instance to grab the bridge ID of the local
> switch.
>
> 7609> show spanning vlan 1000
> VLAN1000
>   Spanning tree enabled protocol ieee
>   Root ID    Priority    5096
>              Address     0011.20d8.7700
>              This bridge is the root
>              Hello Time   2 sec  Max Age 20 sec  Forward Delay 15 sec
>
>   Bridge ID  Priority    5096   (priority 4096 sys-id-ext 1000)
>              Address     0011.20d8.7700   <-- Switch bridge ID
>              Hello Time   2 sec  Max Age 20 sec  Forward Delay 15 sec
>              Aging Time 300
>
> ....
>
> List the local bridge ID for all configured VLAN STP instances.
>
> 7609> show spanning bridge
>                                                    Hello  Max  Fwd
> Vlan                         Bridge
> ID              Time  Age  Dly  Protocol
> ---------------- ---------------------------------
> -----  ---  ---  --------
> VLAN1500           5596 (4096,1500) 0011.20d8.7700    2    20   15  ieee
> VLAN1501           5597 (4096,1501) 0011.20d8.7700    2    20   15  ieee
> VLAN1502           5598 (4096,1502) 0011.20d8.7700    2    20   15  ieee
> VLAN1504           5600 (4096,1504) 0011.20d8.7700    2    20   15  ieee
> VLAN1505           5601 (4096,1505) 0011.20d8.7700    2    20   15  ieee
> ...
>
>
>
> Amol Sapkal wrote:
> > Hi,
> >
> > I was going through my network's STP setup and suddenly I realized that
> I
> > wasn't aware of any command that would let me know the switch MAC that
> takes
> > part in the root bridge selection procedure.
> >
> > Have sifted through a lot of Cisco pages, but unable to hit the correct
> one.
> > Any ideas?
> >
> >
> >
>
> --
> ===================================================
> Clinton Work    clinton at scripty.com
> Calgary, AB
>



-- 
Warm regards,

Amol Sapkal

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