Solved: Cisco vss - connect from access switch with no etherchannel

carl_townshend · ‎05-08-2012

Hi all

If I dual connect my access switch to my 6509s running vss, what will happen, will spanning tree still block one of the ports if I don't set up an etherchannel?

Cheers

Carl

nikolasgeyer · ‎05-09-2012

Assuming a basic topology where there is no VLAN trunking etc going on then yes, STP will block one of the links as you have created a layer 2 loop.

If the links were VLAN trunks and carrying all VLAN's on both links, the above blocking scenario would also apply.

If the links were VLAN trunks and only carrying a subset of VLANs on link #1 and another subet on link #2 (e.g. VLAN's 100 and 110 on link 1 and VLAN's 200 and 210 on link 2) then no blocking would occur as there would be no layer 2 loop.

That should cover off pretty much all the scenarios you could use

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nikolasgeyer · ‎05-09-2012

Assuming a basic topology where there is no VLAN trunking etc going on then yes, STP will block one of the links as you have created a layer 2 loop.

If the links were VLAN trunks and carrying all VLAN's on both links, the above blocking scenario would also apply.

If the links were VLAN trunks and only carrying a subset of VLANs on link #1 and another subet on link #2 (e.g. VLAN's 100 and 110 on link 1 and VLAN's 200 and 210 on link 2) then no blocking would occur as there would be no layer 2 loop.

That should cover off pretty much all the scenarios you could use