[c-nsp] Spanning-Tree question

[Ben Steele]

It should eventually go into a blocking state as the port still  
participates in STP in portfast mode, this can take 30-50 seconds  
though, not sure if you've left it that long?

On a side note, if you have Administrative control over both devices  
and they are in different VTP domains already why not run the links  
between the 2 business's as Trunks with vlan filtering, that way you  
can load balance the 2 vlans with priority over the trunks as well as  
redundancy.

Ben

On 01/02/2008, at 3:51 PM, Aaron R wrote:

> Yes some access ports were portfast! Silly me!
>
> If any of those access ports are in port fast does this mean that  
> spanning
> tree will not work properly? I know portfast will put the ports into  
> instant
> forwarding mode but it should still receive bpdus in order to make a
> decision on what ports are blocked / forwarding yes? Or because they  
> are
> forwarding straight away it doesn't listen to these bpdus in order  
> to make
> this decision.
>
> Cheers,
>
> Aaron.
>
> -----Original Message-----
> From: Ben Steele [mailto:ben at internode.com.au]
> Sent: Friday, February 01, 2008 2:08 PM
> To: Aaron R
> Cc: cisco-nsp at puck.nether.net
> Subject: Re: [c-nsp] Spanning-Tree question
>
> Do you portfast enabled on those access ports?
>
> On 01/02/2008, at 3:31 PM, Aaron R wrote:
>
>> Hi Guys,
>>
>>
>>
>> Ive got a problem that I am hoping someone can have a look at. I
>> currently
>> have four 3750's. Two belonging to one business unit and two
>> belonging to
>> another. Each group of switches is running a separate VTP domain /
>> VLAN
>> database.
>>
>> I am running PVST however when I connect the final link between the
>> four
>> switches there is a loop and spanning tree doesn't block any of the
>> ports.
>> Would anyone have any clue as to why this would be happening? Could
>> it have
>> something to do with the link between the Business units being on
>> separate
>> VLANs? We don't want the possibility of VLAN corruption occurring
>> hence the
>> different VTP domains. Currently I am shutting down one of the
>> uplink ports
>> to Business A to remedy this problem. Please see the diagram below.
>>
>>
>>
>> Cheers,
>>
>>
>>
>> ------------------------
>> ------------------------
>>
>> | 3750 Switch 1  |------- Trunk ------ | 3750 Switch 2  |
>>
>> |  Business A     |                        |  Business A     |
>>
>> -------------------------
>> -------------------------
>>
>>          |   VL 50                                   |   VL 50
>>
>>
>>          |                                              |
>>
>>          |   VL 100                                 |    VL 100
>>
>>
>> ------------------------
>> ------------------------
>>
>> | 3750 Switch 3  |------- Trunk ------ | 3750 Switch 4  |
>>
>> |  Business B     |                        |  Business B     |
>>
>> -------------------------
>> -------------------------
>>
>>
>>
>>
>>
>> Aaron.
>>
>>
>>
>>
>>
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>