We're Sorry, Full Content Access is for Members Only...

If you like to keep on reading, Become a Member Now! Here is why:

  • Learn any CCNA, CCNP and CCIE R&S Topic. Explained As Simple As Possible.
  • Try for Just $1. The Best Dollar You've Ever Spent on Your Cisco Career!
  • Full Access to our 651 Lessons. More Lessons Added Every Week!
  • Content created by Rene Molenaar (CCIE #41726)

451 Sign Ups in the last 30 days

100% Satisfaction Guaranteed!
You may cancel your monthly membership at any time.
No Questions Asked!


Forum Replies

  1. Hi Thomas,

    1. I would prefer BPDU guard on the access layer switches towards the hosts. You don’t want to see any BPDUs from the hosts, if you see them then someone has been messing with bridge mode (bridging two NICs) or they connected a switch, one exception could be a wireless access point. Some of those send BPDUs. If you have BPDU guard enabled, there’s no need to use root guard since a BPDU triggers a violation.

    We use root guard on interfaces where we DO want to receive BPDUs from but we don’t want to accept a root switch on these interfaces.

    1. Take a look
    ... Continue reading in our forum

  2. Mohammad,
    Perhaps you are thinking that should a user plug in a switch that has a superior Bridge ID to the Core’s, then all users will be affected by the Root Guard putting the Access layer’s connection to the Distribution layer in “Root inconsistent” state?

    This won’t happen if you do as Rene suggested and make sure that all of your user facing ports on the Access switches have BPDU guard enabled. If you do that, then any BPDU received, whether it is superior or inferior, will trigger that port to go into an err-disabled state. Think of Root Guard as being

    ... Continue reading in our forum

  3. Hi,

    I think this sentence is very clear in Cisco Web:

    “This root-inconsistent state is effectively equal to a listening state. No traffic is forwarded across this port. In this way, the root guard enforces the position of the root bridge.”


  4. Hi Andrew,

    In the same topology, assume that bpdu guard is configured on access switches interfaces to hosts, root guard is configured on distribution switches interfaces to access switches, and core switches interfaces to distribution switches. If your example 1) a new Distribution switch is plugged in with a superior BPDU would happen:
    1)How would it change the entire spanning-tree topology? Could you give the steps how would it be root bridge?
    2)Would our core switch which was root before, would remain root, or would it start to see new distribution switch a

    ... Continue reading in our forum

  5. You could use it to protect your core/distribution layer switches. If you want to ensure one of your core switches always remains the root, then you could use this to protect yourself from someone (accidently) configuring a distribution switch as the new root bridge. You can also protect your distribution switches from selecting an access layer switch as the new root bridge.

17 more replies! Ask a question or join the discussion by visiting our Community Forum