1) design the network to not have loops (not always possible); use LACP and
stacking technologies to provide the redundancy without messing with
spanning tree if possible.
2) enable spanning tree. multiple-spanning tree is the latest incarnation
and has the most flexibility, but is the hardest to configure. rapid
spanning tree is probably the most-compatible and least-effort and best
second choice. (this is where BPDUs come in). it works on all the major
vendors.
3) enable bpduguard on edge ports. A command like spanning-tree rstp
edge-port bpduguard (or similar) will disable a port that only a
workstation should be plugged into. When a switch gets plugged in, it will
send out a BPDU and your switch should disable the port in response, thus
preventing a loop. In a network where users might be tempted to plug things
in like this, you can protect yourself this way.
4) avoid unmanaged switches. You won't be able to configure things very
easily and will be setting yourself up for problems. If you must use them,
use them only at the edge and not in the core of your network. (only one
uplink)


On Fri, Feb 24, 2012 at 4:49 PM, Chuong Dao <[email protected]> wrote:

> I just spent about 2 hours trying to isolate at loop caused by and
> ex-employee(kidding).
>
> I am aware of some methods out there with HP and Cisco switches like BDPU,
> or loop-protect in HP. What do you think the best solution for this using
> those cheap switches without such features?
>
> I also looking at limiting MAC address per port on Cisco switches. Do you
> know what's the cheapest model that supports this feature?
>
> Thank you for your inputs.
>
> -CD
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