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New Member

spanning tree questions

Hi all

I would like to know if any one can help, I have 2 cat 6509's connected via a 2 x 10gig trunk link, which carries all the vlans between the switches. These are running RSTP. These then plug into a nortel 8600 via 2 links, 10 vlans on one link, 10 vlans on the other, all vlans can be seen on all switches. The nortel is running 1 spanning tree instance for all vlans, it is normal STP. whwn we made the core live, we did not make the new 6500's root and root secondary. I can see that when I look on certain vlans from the 6500's, the root port is going towards the Nortel switch, the nortel switch has lots of other switches hanging off it with single links, so I think that some of the edge switches is providing the root for some vlans.

I would like to make the cisco 6500's root for these vlans, I am worried what will happen, I dont want any blocking on the etherchannel between them.

and also dont know what the effects will be as there are 2 different spanning trees running.

Can anyone help here? and also I read about the spanning trees being tunneled somehow through the nortels single instance, so is the info I read saying that all the spanning tree pvst bpud's still get sent out the link to the nortel, and if there was a PVST switch the other side of the nortel, would it see the pvst bpdu's?

what does it mean my tunneling through the STP cloud ?

hope someone can clear these up for me

cheers

3 REPLIES
Hall of Fame Super Silver

Re: spanning tree questions

Hello Carl,

>> what does it mean my tunneling through the STP cloud ?

simply that the Cisco PVST+ BPDUs used on an 802.1Q trunk are proprietary with a different multicast destination and different encapsulation and are treated as user traffic by 802.1D standard switches

>> d if there was a PVST switch the other side of the nortel, would it see the pvst bpdu's?

yes

Hope to help

Giuseppe

New Member

Re: spanning tree questions

is this because pvst bpdu's are multicast, thus sent out of all ports including

the nortel, so the nortel will just forward them out ?

Hall of Fame Super Silver

Re: spanning tree questions

Hello Carl,

>> is this because pvst bpdu's are multicast, thus sent out of all ports including

the nortel, so the nortel will just forward them out ?

yes

Hope to help

Giuseppe

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