3750 stackable switches etherchannel to core switches

[Horacio Gutierrez]

Hello,

If I have two stackable switches one switch uplinks to one 6509 core switch and the other connection uplinks to another 6509 core switch, and also the other stackable switch does not connect to the core switches. Because I am using hsrp and also we are not using vss then one uplink to the core is not in used only ones is so then how does creating an etherchannel between does two uplinks to both core switches benefit me in anyway such as more bandwith and using both uplinks at the same time or I'm I wrong, can someone explain that to me.

Thanks.

[Reza Sharifi]

Hi,

If I understand your question, you are saying, you have 2 3750 switches that are stacked, but you are only uplinking one of them to 2 6509 core switches and you are running HSRP on the 2 core 6509 switches, is that right?

[Horacio Gutierrez]

Correct.

[Marvin Rhoads]

You're correct that your current configuration will only use one of the two connected links at a given time. To use more than one link (assuming a single VLAN in the stack) you'd need two or more links in an Etherchannel to a given core switch. You could, for instance, make four links total in two Etherchannels.

Another alternative would be to have multiple VLANs in the 3750 switches and configuring spanning tree such that one VLAN is forwarding to backbone switch A and the other VLAN is forwarding to backbone switch B. In the even of link failure, both VLANs would use the remaining active link.

Hope this helps.

[Horacio Gutierrez]

Is there any advantage at all for the configuration with a L3 etherchannel with one uplink to a core swich and another uplink to the other core switch?

Thanks.

[Reza Sharifi]

Etherchannel just gives more pipes to use.  Instead of one link, you bundles multiple interfaces together, so one flow uses and link and another flow used a different link.

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HTH

[Horacio Gutierrez]

But in my setup that would not be the case I would need vss for this configuration to work, right?

[Marvin Rhoads]

Right. If you want Etherchannel to give you additional bandwidth, plus physical redundancy to mupltiple non-VSS core switches, then you need multiple Etherchannels.