1 2 Previous Next 19 Replies Latest reply: Nov 11, 2019 7:38 AM by Ing_Percy RSS

    FLP with auto-negotiation

    Mohamed

      Hi CLN

       

      flp-pulse.gif

       

      flp-code.gif

       

      if we enable (auto negotiation)feature for speed and disable it for duplex mode , is that means (auto negotiation) won`t use FLP ?

        • 1. Re: FLP with auto-negotiation
          ciscodaze1

          No, speed it still determined by FLP, even if you hard code the duplex (assuming you make duplex match on both ends of course). My understanding from what I have read is that speed is completely determined by electrical patterns, whereas duplex involves some kind of messaging between the ports advertising their duplex mode.

           

          I think thats why your charts show Clocking and Data patterns...I would assume the Data part refers to the codes listed in the box below which seems to me would include the duplex information, as well as other information.

           

          I don't understand your focus on things like FLP...this is not on any exam, and it will not help you get a job. If its just curiosity, of course I understand that.  But I would spend my time on more practical things (stuff in the books, and in the blueprints).

          • 2. Re: FLP with auto-negotiation
            Mohamed

            Kev

            Thanks for your reply

            do you mean stop and don`t continue ? OR what ? i don`t know

            • 3. Re: FLP with auto-negotiation
              ciscodaze1

              Im just saying focusing on stuff like this is fun and interesting, but in the long run it wont really help you get a job or pass an exam. Especially since your first exam will be for CCNA, and your first job interview will not involve questions at this level of detail.

               

              Not trying to discourage you from learning all kinds of stuff...go for it.

              • 4. Re: FLP with auto-negotiation
                ciscodaze1

                If you want to see how complicated this stuff really is, take a look at this!

                https://www.iol.unh.edu/sites/default/files/knowledgebase/ethernet/Copper_ANEG_JEFF_LAPAK.pdf

                 

                Fortunately, all we need to do is remember a couple of basic setting to make our connections work

                • 5. Re: FLP with auto-negotiation
                  ciscodaze1

                  Moh, this is from the current CCIE book:

                   

                  moh.JPG

                  • 6. Re: FLP with auto-negotiation
                    Martin

                    Speed and Duplex are the same negotiation process but they do in sub-steps:  speed is first; then duplex next.  in other words , duplex setting depends on the speed.  So, you could not really say turn off speed negotiation but kept duplex auto , right


                     

                     

                    As I wrote in other post:


                    Auto negotiation allows negotiate speed and duplex settings at physical layer. Auto negotiation uses pre-set Priorities when matching speed and duplex mode.  it starts from the highest to lowest: 1000 full, 1000-half, 100 full, then 100 half, 10 full, ending on 10 half.


                    It is like speed takes precedence over duplex since it is more critical.  Therefore, I do not completely agree that Speed and Duplex are separate negotiation processes; Duplex depends on Speed.

                     

                    Updated order is now as follows :

                    Priority

                    Upon receipt of the technology abilities of the other device, both devices decide the best possible mode of operation supported by both devices. The priority among modes specified in the 2018 edition of 802.3 is as follows:[10]

                     

                    1. 40GBASE-T full duplex
                    2. 25GBASE-T full duplex
                    3. 10GBASE-T full duplex
                    4. 5GBASE-T full duplex
                    5. 2.5GBASE-T full duplx
                    6. 1000BASE-T full duplex
                    7. 1000BASE-T half duplex
                    8. 100BASE-T2 full duplex
                    9. 100BASE-TX full duplex
                    10. 100BASE-T2 half duplex
                    11. 100BASE-T4 half duplex
                    12. 100BASE-TX half duplex
                    13. 10BASE-T full duplex
                    14. 10BASE-T half duplex

                     

                    In other words, among the modes that are supported by both devices, each device chooses the one that is the topmost in this list.

                     

                    source : Autonegotiation - Wikipedia

                    • 7. Re: FLP with auto-negotiation
                      Mohamed

                      Hi martin , How are you friend ?

                      thanks for your reply

                      Speed and Duplex are the same negotiation process but they do in sub-steps:  speed is first; then duplex next.  in other words , duplex setting depends on the speed.  So, you could not really say turn off speed negotiation but kept duplex auto , right


                      if we do this :-

                       

                      int G0/0

                      speed 10 --------> this imply (DISABLE) auto negotiation with speed . force interface to send/rcv 10Mbps ONLY , even interface supports 1000Mbps

                      speed 100 ------> this imply (DISABLE) auto-negotiation with speed .force interface to send/rcv 100Mbps ONLY , even interface supports 1000Mbps

                      speed auto ------> this means ( enable )auto-negotiation

                       

                      duplex half -------> this imply (DISABLE) auto negotiation with duplex mode . force interface to act as half duplex mode even G0/0 has capability to do full duplex mode

                      duplex full ---------> this imply (DISABLE) auto negotiation with duplex mode . force interface to act as full duplex mode 

                      duplex auto ---------> this means (enable ) auto negotiation with duplex mode



                      in other words , 2 command only support auto negotiation to run (duplex auto),(speed auto) commands



                      is that correct ???

                      • 8. Re: FLP with auto-negotiation
                        Parvesh

                        Agree with Kev as the topic is interesting but not leading to blueprints of the exam. In majority, the question is why would somebody want to manually configure if it can be automatically negotiated ?

                         

                        Yes, there are times when autonegotiation may not work as expected. It may not work always and will need bit more understanding and hard coding.

                         

                        I would refer bit older but hope is a helpful post -

                        Poll: Do you hard code your duplex settings or rely on autonegotiate?

                         

                        For critical operations, I would suggest hard code it and leave the auto negotiation to troubleshooting only. That's what I learned almost 10 years back when a server wont connect with autoneg but with hard coding ( no changes at either end except).

                         

                        Hope it helps.

                        • 9. Re: FLP with auto-negotiation
                          Steven Davidson

                          Mohamed wrote:

                           

                          Thanks for your reply

                          do you mean stop and don`t continue ? OR what ? i don`t know

                          You need to know the following:

                           

                          1.) Compare two outputs and determine whether or not a duplex mismatch has occurred.

                          2.) Know how to fix the problem if you find it.

                           

                          I can count on one hand the number of times I have come across a duplex mismatch situation.  It usually happens when something gets upgraded (like a switch or WAN circuit).

                          • 10. Re: FLP with auto-negotiation
                            ciscodaze1
                            Therefore, I do not completely agree that Speed and Duplex are separate negotiation processes; Duplex depends on Speed.

                             

                            Martin, I think you are correct.  I found the page where Mohamed found those diagrams, and it is the clearest and most helpful explanation of FLP I have seen yet: Ethernet Fundamentals

                            • 11. Re: FLP with auto-negotiation
                              Mohamed

                              Priority

                              Upon receipt of the technology abilities of the other device, both devices decide the best possible mode of operation supported by both devices. The priority among modes specified in the 2018 edition of 802.3 is as follows:[10]

                               

                              1. 40GBASE-T full duplex
                              2. 25GBASE-T full duplex
                              3. 10GBASE-T full duplex
                              4. 5GBASE-T full duplex
                              5. 2.5GBASE-T full duplx
                              6. 1000BASE-T full duplex
                              7. 1000BASE-T half duplex
                              8. 100BASE-T2 full duplex
                              9. 100BASE-TX full duplex
                              10. 100BASE-T2 half duplex
                              11. 100BASE-T4 half duplex
                              12. 100BASE-TX half duplex
                              13. 10BASE-T full duplex
                              14. 10BASE-T half duplex

                               

                              i notice that 40G and 25G and 10G and 5G and 2.5G interfaces are NOT supported half Duplex, WHY ?

                              • 12. Re: FLP with auto-negotiation
                                Martin

                                int G0/0

                                speed 10 --------> this imply (DISABLE) auto negotiation with speed . force interface to send/rcv 10Mbps ONLY , even interface supports 1000Mbps

                                speed 100 ------> this imply (DISABLE) auto-negotiation with speed .force interface to send/rcv 100Mbps ONLY , even interface supports 1000Mbps

                                speed auto ------> this means ( enable )auto-negotiation

                                 

                                duplex half -------> this imply (DISABLE) auto negotiation with duplex mode . force interface to act as half duplex mode even G0/0 has capability to do full duplex mode

                                duplex full ---------> this imply (DISABLE) auto negotiation with duplex mode . force interface to act as full duplex mode 

                                duplex auto ---------> this means (enable ) auto negotiation with duplex mode


                                that looks correct;  To enable auto-negotiation of speed and duplex use commands: speed auto , duplex auto 



                                • 13. Re: FLP with auto-negotiation
                                  Mohamed

                                   

                                  Speed and Duplex are the same negotiation process but they do in sub-steps:  speed is first; then duplex next.  in other words , duplex setting depends on the speed.  So, you could not really say turn off speed negotiation but kept duplex auto , right

                                  maybe you`re Not correct because speed 100 command and duplex half command are a separate commands .

                                  so , why you said these lines ? the 2 commands for duplex and speed are completely separate from each others

                                  • 14. Re: FLP with auto-negotiation
                                    Ing_Percy

                                    Hi!

                                     

                                    Although the commands are separate, the definition for speed/duplex is under the same process. If you have seen the Autonegotiation table of Cisco page, you can see both are mutually relationed.

                                     

                                    Regards!

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