VC & LACP/Etherchannel with Cisco 3750 switches & Stackwise

[Paul_637]

I recently learned about the "Stackwise" capabilities of the switches we have our VC modules rigged up to and think we can have the best of both worlds with an active/active LACP uplink with full switch redundancy!

Based on the document I found at http://www.cisco.com/en/US/prod/collateral/switches/ps5718/ps5023/prod_presentation09186a0080161372.pdf, you can create an etherchannel spanning multiple switches.

In that case, given a scenario with 4 stacked switches, should we not be able to legitimately create two LACP groups - one per VC module - but spanning all four switches with two VC ports per switch?

This would give us theoretically FULL available bandwidth through each VC module thus giving us absolute maximum available bandwidth (using 1Gb links) as well as full redundancy (max ports lost with any one switch being two per VC module).

Or, am I missing something else?

Regards,

Paul

[Jeff Allen_5]

You don't need stackwise to get an active/active configuration with VC. All you need to do is create different VC networks with uplinks (only) on each individual module. VC won't let you use the same names in more than one place, so just add a "2" or a "B" to the 2nd name. VC will automatically create a 2nd (or 3rd, or 4th) LACP channel group to the upstream switches. Don;t so any crossover cabling or anything as LACP needs the same physical device on BOTH sides (not just the stackwise side). Just because stackwise gives you the ability to create channels that span switches, it doesn't mean the other side can (Cisco is using proprietary technology to do this). The 802.3ad spec says that a single physical device must be on each side of the link. Cisco is making their side look like a single device, but VC is still 2 (or 3 or 4, etc) different physical devices.

Hope this helps

[Paul_637]

Yep, I'm aware I don't need Stackwise. I currently have multiple vNets configured in various ways (some with uplink ports only on one VC-Eth module with LACP for maximum bandwidth, others spread over multiple VC-Enet modules for maximum availability where bandwidth isn't such an issue.

I came across the Stackwise doc recently and hoped I might be able to get the best of both worlds - full bandwidth (active/active) over multiple switches :)

I guess there are no plans for HP support of Ciscos tech then? :)

Regards,

Paul