[F10-nsp] Multiple ports hanging/dropping on on S50

[wwbach at gmail.com]

We've recently picked up three used force10 SA-01-GE-48T switches.  We're
experiencing random issues where is seems like a significant portion of the
switch stack drops connections to the devices connected.  This is happening
maybe a couple of times a day.

Here is some more info:

I only know enought to be dangerous -- we have a networking consultant
working on it who probably is better with cisco gear but has some f10
experience.

The swithes are stacked using two stacking cables -- 1 to 2 and 2 to 3.
 This seems like this is a supported configuration (cascade) according to
this web page:


http://www.force10networks.com/CSPortal20/TechTips/0057_HowDoIStackSSeriesUnitsTogether.aspx

but maybe we *need* a cable from switch 3 back to 1 (ring)?

All the switches are running SFTOS  2.5.2.2 with QOS, Multicast, Stacking
and Routing.

Nothing unusual in the log.  A few interfaces going up and down but not
really corresponsing to when we are experiencing issues.

No errors in "show stack-port diag".

We took one of the switches out of the mix and things seemed to be better
but not perfect.

When the problem occurs, everything comes back to normal after a couple of
minutes.

There are several vlans configured.  One vlan where most of the
communication is confined to the vlan has not seemed to have any problems.

When the problem occurs, it seems to affect ports on multiple switches in
the stack.

Spanning tree routing is enabled as is OSPF.

Another thing worth mentioning is that the we had some issues configurring
multicast routing.  We wanted to use sparse mode PIM but couldn't get it
working with a cisco router.  We ended up getting a multicast proxy working
-- not sure what this really means.

Most of the gear attached to the stack is either broadcom of intel chipset.

Any ideas on how to futher debug this issue or what to look at?  Thanks.  --
Bud
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