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using a third party non-mangebale switch in a cisco environment


We have a cisco powered network consisiting of a catalyst 6513 as core switch and edge switches as catalyst is a converged network with voice and data.power ove er ethernet is used to give power for phones.

Let me explain my problem. A developer needs 5 pcs to be connected to the network. Butut he has only two network points available . so to connect rest of the pcs he is depending on a third party non-mangeble switch. can this practice be encouraged ? if not what is the alternate solution? what advice should be given to the developer ?please respond at your earliest convenience.



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Cisco Employee

Re: using a third party non-mangebale switch in a cisco environm

Hi Pradeep,

The most important consideration with a non-managed switch is that (depending on what type of switch, and what features it offers), the managed portion of the network must be protected from any problems that can be caused by the unmanaged switch, such as inadvertently connecting the unmanaged switch to two network ports, causing a layer 2 loop that can bring down the entire network. Additionally, I have seen cases where such a switch runs spanning tree and based on the root priority and MAC address in the BPDUs it sends, caused a STP reconvergence and/or assumes root.

There are many ways to protect against these situations. First, we want to treat such as switch as an entity that is not part of the network. In other words, it should not be part of the Spanning Tree topology.

First, we'll want to enable Portfast on the interface that the unmanaged switch will connect to. In addition, the STP PortFast BPDU guard enhancement allows you to enforce the STP domain borders and keep the active topology predictable. The devices behind the ports that have STP PortFast enabled are not able to influence the STP topology. At the reception of BPDUs, the BPDU guard operation disables the port that has PortFast configured. The BPDU guard transitions the port into errdisable state, and a message is generated.

More on the feature here:

It's generally good practice to enable this feature on all user ports to guard against these situations where users connect rogue devices to their network ports.



New Member

Re: using a third party non-mangebale switch in a cisco environm

dear bobby,

Thanks a lot for the quick response. My problem is that developers are not in to networking so they do'nt accept this . I want a suggestion from you stating that usage of third party devices should be discouraged. if it is from cisco i can use it as a proof.