Linking two Procurve switches together

So - the scenario is this!  We currently have an HP Procurve 5412zl switch (fully populated).  this has a few VLANs configured, the main ones being for Data and the VoIP phones.  We also have some VLANs setup up for Wireless networks etc.  

We now need to add a second switch to allow the capacity for extending the office; so i have got a 5406zl2 switch, together with 2 x 20GB + 2 x 10GB SFP modules and some SFP+ cables to connect them together.  The plan is to use LACP to utilise the full 20GB capability between the two switches that the SFP+ ports can provide (one module per switch).

However - I am reading a lot of conflicting and confusing information about how to approach it - most people seem to be advising against LACP, or if i do use it, to enable spanning tree protocol - which of course i can't due to using a MITEL IP phone system...

Can anyone offer any decisive advice on this please?
Amaze_ITAsked:
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asavenerCommented:
If you're absolutely sure that you're not going to have forwarding loops, then you can avoid spanning tree.  

I think the concern is that if LACP negotiation fails you could have two separate links, instead of one portchannel link, which would cause a forwarding loop if spanning tree is not enabled.

Can you advise more on why the MITEL IP phone system prevents the use of spanning tree?

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JustInCaseCommented:
You can use STP, but it is not recommended to use it since you have IP phones.
You should use MSTP, and enable portfast on ports that have end hosts attached. But, be careful, it is easy to make configuration error with MSTP.

Also you could use LACP, but sometimes (not too often) it can cause issues where one side believes it is in port channel and other thinks it is not, so it may lead to network loop. But when that happens...
Amaze_ITAuthor Commented:
use of IP phones (certinaly with Mitel) with STP enabled causes the phones to fail due to the timeout on DHCP requests made by the phones; these timeout before a connection is allowed by STP on the port.

I did think about using portfast, but pretty much ever single port is connected to an IP phone, and laptops docks/desktops are connected through the back of them.
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asavenerCommented:
Ah.  You're having to work around a defective product.

In that case, I would suggest portfast with BPDU guard, and security set to allow only two MAC addresses.
Amaze_ITAuthor Commented:
thanks asavener - are there any links you could direct me to for this method?  Switch programming is not the strongest point for me - and unfortunately i have not go the time to experiment with this solution (7 days to implement, test and go live)....i'm struggling to understand what to do with regards to the VLANS as well - do i set upi the Voice and Data vlans on the second switch and give them a different VLAN numberor the same etc?
asavenerCommented:
Doesn't your phone vendor have a recommended port configuration?
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