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VLAN's extended through stacking?

Hi, tomorrow I must configure four VLAN in many switches and I would like to know if the VLAN are extended from one switch to another if they are stacked.

Many thanks in advance

5 REPLIES

Re: VLAN's extended through stacking?

Hi,

AFAIK, not unless you are using the new 3750 switches.

You need trunk connections between switches with VTP domain configured to automatically extend VLANs defined on one switch (VTP server) to others (VTP clients).

It is possible to use GigaStack GBICs but FULL-DUPLEX connections only.

GigaStack half-duplex connection doesn't support trunk connection at all (trunks need point-to-point connection).

Regards,

Milan

Re: VLAN's extended through stacking?

Just a caveat to the GigaStack comment from Milan. You CAN configure a cascaded GigaStack link as a Trunk (ISL or dot1q); it doesn't have to be point-to-point. The only downside is the Cascaded connection will only work in half-duplex (like a hub) so as the traffic increases so do collisions and the useable throughput. This is not applicable on point-to-point Full-Duplex links as collisions don't occur here.

Andy

Re: VLAN's extended through stacking?

Re: VLAN's extended through stacking?

Milan

In response to your question on whether we have tested VLAN Trunking Over a Cascaded GigaStack link - Yes, I have deployed a few networks where this type of topology is used. Ideally there would be no stacks at all (stacking sucks) but where cost is an issue, needs must.

With the newer switches (2970 & 3570?) Cisco have taken a different approach and used a proprietary stacking port so all the Issues with the Stack Port being Ethernet should (hopefully) be eliminated.

Andy

Re: VLAN's extended through stacking?

Andy, you were correct.

Trunking works on GigaStack half-duplex connection.

But it's necessary to use switchport mode trunk and switchport nonegotiate interface configuration commands.

See http://www.cisco.com/univercd/cc/td/doc/product/lan/c3550/12114ea1/3550scg/swvlan.htm#1096213 for details.

Regards,

Milan

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