Stacking Procurve 2900s

[Slu]

Hi All

At the centre of my network I have a HP 2900-24g (24gig ports + 2x stacking 10gbe ports) switch.  A few weeks ago this switch failed and had to be replaced under support (and is now back in place again working fine).

Eventually, I have managed to fix the previously failed switch and as such now have 2x 2900-24g switches.

Im starting to consider stacking the pair together using the 10 gbe ports (CX4 plus cable) - these can be stacked and managed from a single IP - however.. my query is this:

Im in the process of starting to use LACP / bonding dual Gb network connections from our servers, however it seems a little pointless to run both connections to a single switch and would be much better spread across a pair of stacked switches.

If i stack both the 2900's together, can I still run LACP across the pair of stacked switches??

thanks for any help!  I just wanted to check before I go out an buy a 10gbe module for the 2nd 2900.

[RyanBiddle]

Hi, I came here with a question, but saw yours un responded to...

Her's what I got for what it's worth

(admittedly based on an HP A5500 stack <6node>, but lesson learned is worth telling I think.)

:

I've been through the stacking thing, what they don't tell you is that when it comes to software upgrades you're dealing with the whole stack, and trying to maintain availability to dual homed hosts and becomes an impossibility.

this is all relevent, if your goal is to never to have to tell the boss the network is going down for maintenence.

Newer switches have orchestrated upgrades, but same problem.

(with HP

staying unstacked can mean less 'managment', albieat with more managment (shortcuts and commands)

With three, assuming your have no X2 modules, I'd create a 2x10GB LAG using the CX4 connectors. between the two.

CX4 DAC cables are cheap(er)

[if you're saturating a 20GB LAG, pat yourself on the back, and buy a Nx9K]

Remeber, a CX4 is 4x2.5GB channels, so each theeaded copy job for exacmple would be limited to 2.5GB. Something to consider when planning backups.

You can throw the appropriate X2 module to get a 10GB channel, (or so I am told)

Keep the third as a LAB/Configered Spare.

-Ryan

[Richard Brodie_1]

You can't do 'true' stacking on most Procurves; you can manage them with a single IP using the stack protocol but that doesn't require a direct connection between the switches. It doesn't allow additional functionality, like split LACP or anything like that. You can with 2920s and stacking modules but that's two generatations of hardware later.

@Ryan "CX4 is 4x2.5GB channels". This is true at the physical level in that it's 4 pairs, however, you could say the same about 1000BASE-T. They are both true 10G interfaces for practical purposes.

Edit: I obviously had a brain failure and lost a factor of 10 when I wrote that last sentence.

[Slu]

thanks for the reply both - i think I had come to the conclusion that would be the case regarding the stacking - unfortunate but not much I can do.

On the LACP front, splitting across two switches pretty much leaves me with STP - and as the backups wont be using more than a single 1gbps link, then its kinda pointless me using a 10gbps between the two 2900's.

think im just going to end up with the two 2900's trunked together using LACP for 2gbps, then remaining servers connected to either using STP.

cheers

S

[Vince-Whirlwind]

They should really use the words "stacking" for stacking and "management cluster" for what the Procurves call "stacking".