9 Replies Latest reply: Oct 30, 2008 6:38 AM by Conwyn RSS

    What topology is best?


      I want to practice vlan trunking, mac, ip,port discovery and running protocols . I have two routers and two switches. should I connect the two switches by one cable to any port on either switch and then connect router 1 to switch 1 thru router 1's AUX port to one of switch 1's ports then router 2 to switch 2 in the same fasion, then console in thru one of the routers, then practice on my trunking and routing that way? or is there a better set up?

        • 1. Re: What topology is best?


          Hi Jason,



          To learn the specified topics, one should always try with different topologies.



          I think different topologies help you understand the concepts really well.



          I feel that NO single topology is BEST for learning and understanding every thing.



          Here are some sample topologies that you can try with 2 routers and 2 switches.



          In these samples, I have used Crossover, straight-thro and serial-cables.



          You can CONSOLE to any device depending upon what and where do you want to experiment with..



          I Hope this helps..



          • 2. Re: What topology is best?

            Thank you for the reply. I did'nt really know that it could be so flexible. I think these topologies will really help or confuse me more............. was I right in my ptrvious connection methods? exapmle ( routers 1's AUX to Switch 1 fao/2) and another question i have is, can switches trunk with a router between them?

            • 3. Re: What topology is best?


              Hi Jason



              You connect the router Ethernet port to the switch Ethernet ports.



              You can connect the router AUX to another router AUX with a roll over cable.



              You can connect a router Ethernet to a switch as a trunk. See the router on a stick document.



              If you need help come back.



              Regards Conwyn









              • 4. Re: What topology is best?


                You asked, " can switches trunk with a router between them? "



                The answer is YES. This is possible.



                This particular topology can be useful when you want inter-vlan communication without using Router-On-A-Stick Model.



                Check out the following link for above topology as well as some more useful information:









                As far as Cable Connections are concerned, I think Conwyn has already answered that question.






                • 5. Re: What topology is best?
                  Scott Morris - CCDE/4xCCIE/2xJNCIE

                  As a note, without making things truly complicated (way beyond where you want to start!) the router can trunk, but it's designed to do that for routing, not forwarding in the "normal" fashion.



                  The big thing you'll miss out on is spanning-tree. While some may view this as not a bad thing, I suggest that it's a good thing to be familiar with!



                  With that in mind, if you can get your hands on a third switch, so you can design a nicely "looped" topology, that will help you understand the nuances of spanning tree MUCH better!







                  • 6. Re: What topology is best?

                    Thanks for the reply, I have a question about my routers interfaces. My routers are Cisco 2501 and as far as I can tell The interfaces on them are as follows, AUI, Serial 0, Serial 1, Consosle, and AUX. my assumtion is that the AUX interface is my only Ethernet port. Is that true?

                    • 7. Re: What topology is best?

                      Hi Jason


                      AUI = Attachment Unit Interface = Ethernet = DB15 connector

                      CON = Console Port

                      AUX = Modem port or Roll over cable

                      SER = Serial Ports such as X21 V35 = DB60 connector


                      See http://www.cisco.com/en/US/docs/routers/access/2500/2501/software/user/guide/ovr.html and

                      see http://www.2000trainers.com/cisco-ccna-06/ccna-router-ethernet-ports


                      You will need a transceiver which converts from DB15 to RJ45 or co-axial


                      Regards Conwyn

                      • 8. Re: What topology is best?
                        Scott Morris - CCDE/4xCCIE/2xJNCIE

                        While you can indeed do routing over the AUX port, it is not really a simple or recommended way to cable your network! It is designed for connecting a MODEM for out of band management capability.


                        On a 2500 series router, you'll use an ethernet transciever (yup, definitely old-school) to get a whopping 10-meg connection!


                        But it keeps life interesting and a healthy perspective on why current trends are much cooler! hehehe...


                        So in a 2501, you will have one ethernet port and two DB60 serial ports to play with.


                        Good luck on your studies!



                        • 9. Re: What topology is best?


                          Hi Jason



                          As Scott said you can route over your AUX port but you need a rollover cable 1->8 etc



                          Joking but it might be easier to find a cable nowadays than a transceiver.



                          Regards Conwyn



                          interface Async65

                          ip address

                          encapsulation ppp

                          keepalive 5

                          async default routing

                          async mode dedicated



                          line aux 0

                          no exec

                          modem InOut

                          stopbits 1

                          speed 38400

                          flowcontrol hardware