Simple Spanning Tree Question

Posted on 2012-08-29
Last Modified: 2012-08-29

Our network is as follows. A Cisco ASA 5505 -> Linksys SLM 2024 (24 port gig switch) -> Netgear GS724T (24 port gig switch via trunk from Linksys) -> Dell Poweredge 2708 (8 port gig switch via trunk from Netgear). Right now, only the Linksys SLM is running STP. The Netgear supports STP but it is not enabled. I don't believe the Powerconnect switch supports STP. In this environment, would you recommend to leave things as it or make some changes?

We have a very flat network (one broadcast domain) and the STP frames from the Linksys switch are hitting workstations and servers. Is there anyway to disable STP on certain interfaces? Is this anything to be concerned about?

Any input would be great, thank you.
Question by:coldfirenj
    LVL 24

    Expert Comment

    by:Ken Boone CCIE #4649
    In general you always want to run spanning tree on your switches.  The purpose of STP is to prevent a loop from occurring on your network.  If you don't run STP on all your switches, you will not have this protection.
    LVL 21

    Expert Comment

    If possible, I would try to have the Dell connect directly to the Linksys so that the Netgear does not have to handle the extra traffic from the Dell and so the Dell is not dependent on the Netgear.  But since you only have one ASA and one core switch (the Linksys), there is not much for spanning-tree to do.  If your network grows to where it has 2 firewalls or 2 core switches, then you can look at spanning-tree.
      Some switches can turn off spanning-tree, and some can only change various settings while the STP protocol must be left on.  I would leave it on because it keeps the network functional in the event of a cable being connected to the wrong port at some point.
    LVL 24

    Accepted Solution

    eeRoot stated the main reason to run STP in your environment:

    "because it keeps the network functional in the event of a cable being connected to the wrong port at some point."

    You say I would never do that, but the day you are out sick and someone is trying to fix something - it could get connected up and bam you have a loop.

    Author Comment

    I guess my question is... Is STP running on only the Linksys switch doing us any good?
    LVL 24

    Assisted Solution

    by:Ken Boone CCIE #4649

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