Right... The IEEE spec for 802.1Q only allows one STP root for the entire
network topology. Cisco gear allows STP root per VLAN, as does the Nortel
Accelar by use of Spanning Tree Groups.
-Brant.
-----Original Message-----
From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED]]On Behalf Of
Seth Wilson
Sent: Monday, January 15, 2001 5:43 PM
To: [EMAIL PROTECTED]
Subject: Re: Cisco to 3Com Dot1Q trunks and VLANs
If memory serves me correctly, Cisco doesn't support per-VLAN STP in 802.1q,
at least not when the trunk is connected to non-Cisco devices. The Cisco
devices will still keep a per-VLAN spanning tree.
~Seth~
----- Original Message -----
From: "Lance Hubbard" <[EMAIL PROTECTED]>
To: <[EMAIL PROTECTED]>
Sent: Monday, January 15, 2001 3:58 PM
Subject: Re: Cisco to 3Com Dot1Q trunks and VLANs
> This brings to mind a question for the group:
>
> Will Cisco's 802.1Q implementation support per-VLAN STP?
>
> Cheers,
>
> Lance
>
>
> >From: "Chris H" <[EMAIL PROTECTED]>
> >Reply-To: "Chris H" <[EMAIL PROTECTED]>
> >To: [EMAIL PROTECTED], [EMAIL PROTECTED]
> >Subject: Re: Cisco to 3Com Dot1Q trunks and VLANs
> >Date: Mon, 15 Jan 2001 19:41:55 -0000
> >
> >Michale,
> >
> >I have dot1q trunks running across Cisco MDF switches and Nortel IDF
> >switches. We found that Cisco and Nortel run two different versions of
> >Spanning Tree, both of which are 802.1q compliant. The difference
between
> >the two is that Cisco's portfast feature, and Nortel's faststart feature
> >are
> >different, where portfast has a default forward delay of 15 seconds, and
> >faststart doesn't implement the forward delay feature.
> >
> >This resulted in a huge amount of TCN's (topology change notifications),
> >particularly in the morning, when all end users are booting up their pc's
> >and changing to 'forwarding' mode in spanning tree. As a result, we
opened
> >a ticket with Nortel, and they agreed to add forward delay to their
> >switching code to correct this problem.
> >
> >I would check the STP documentation on both vendors, and determine if all
> >the default values are the same, what the default root bridge priority
> >number is with both vendors, who you have configured as your root bridge,
> >etc. I would even plug a sniffer in and capture some traffic... Draw out
a
> >spanning tree diagram, and document your root bridge, and the subsequent
> >switches in the spanning tree. Those are just some suggestions... Hope
you
> >find some results.
> >
> >Chris
> >
> >
> > >From: [EMAIL PROTECTED]
> > >Reply-To: [EMAIL PROTECTED]
> > >To: [EMAIL PROTECTED]
> > >Subject: Cisco to 3Com Dot1Q trunks and VLANs
> > >Date: Thu, 11 Jan 2001 13:02:56 -0600
> > >
> > >I have the opportunity to create this cross platform network and am
> >looking
> > >for
> > >information other than the standard documentation from Cisco and 3Com
to
> > >accomplish this task. The dot1Q trunks appear to be functioning
> >correctly
> > >between the Cisco 6509 and the 3Com 3300, but the VLANs are not
> >performing
> > >optimally. Any helpful information or pointers to sites with
information
> > >would
> > >be greatly appreciated.
> > >
> > >Mike
> > >
> > >
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