2 Replies Latest reply: May 4, 2012 1:09 AM by Daniel RSS

    Dual Ring Topology


      Hello ,


      I have found this questions and two diffecrent resources answers it differently

      In which circumstance are multiple copies of the same unicast frame likely to be transmitted in a switched LAN?

      A. after broken links are re-established
      B. in an improperly implemented redundant topology
      C. when upper-layer protocols require high reliability
      D. during high traffic periods
      E. when a dual ring topology is in use




      One resource says the answer is B , as improperly implemnted redundant tolobplgy means STP is not in use


      and another resource says its E



      Can Anyone help me which one is the moree corrrect answer ? B or E ?

        • 1. Re: Dual Ring Topology
          CiscoLoco - CCIE# 50844

          A dual ring topology in its self doesnt mean you are going to have multiple copies of the same unicast frame, aka loops, it just allows the possibility if its not configured properly.  In my opinion the MUCH better answer is B like a spanning tree misconfiguration on a redundant network.

          • 2. Re: Dual Ring Topology

            Hi Tamer,


            Which certification are you studying for? Reading the question it clearly states:


            "...multiple copies of the SAME unicast frame LIKELY to be transmitted in a switched LAN?"


            If you're studying for the latest CCNA version, it's very very dull information regarding Ring topologies...it's as you may have noticed focused on Ethernet and Star topologies.


            I agree with CiscoLoco, answer B is correct because STP is most likely not enabled.


            Reason: It says in the question that it's using a unicast frame. Then based on the CCNA curriculum it's ethernet, as token ring uses another type of frame called "Token Frame" and also uses Active monitor/standby monitor stations to detect multiple token frames.



            Edit: I may (have!!) expressed myself a bit....confusing, so to avoid confusion....token ring uses a different technique than ethernet and stations are added based on a 5-phase process before they can participate in the ring. Token ring still uses broadcast, unicast and multicast - just wanted to make that clear Tamer ! So to not go into details, it's much much more likely a L2 loop will occur in a Ethernet switched network without STP enabled than it it is in a dual token ring topology but it Can occur and STP should be enabled.