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    frame-relay map ip command

    networkguy09

      Information:

       

      RouterA-(DLCI 100)--------(Frame Relay Cloud)---------(DLCI 200)-RouterB

       

      RouterA# show run

       

      <some output text omitted>

       

      interface serial0/0

      bandwidth 64

      ip address 172.16.100.2 255.255.255.0

      encapsulation frame-relay

      frame-relay map ip 172.16.100.1 200 broadcast

       

      Question: Router A is unable to reach RouterB. Based on the above information, what is most likely the cause of the problem?

       

      Answer:

      incorrect map statement

       

      The local DLCI from RouterA to Frame-relay cloud is 100, which is 200 from RouterB to FR cloud. The local DLCI FR mapping from RouterA to RouterB is as follows: frame-relay map ip 172.16.100.1 100 broadcast.

       

       

       

       

      Is the above answer correct?

        • 1. Re: frame-relay map ip command
          Keith Barker - CCIE RS/Security, CISSP

          Yes, the answer is correct.

           

           

          Think of the PVC as a pipe with 2 ends.  (that part is not so hard to imagine.   It is called a PVC after all. )

           

          Imagine that you are at one end of the pipe, and I am at the other.     The label or DLCI the provider has given me for my end of the pipe is 22.   The label the provider has given to your end of the pipe is 33.     My IP address is 10.0.0.22.   Your IP address is 10.0.0.33.   For you to send a packet to me (destined for 10.0.0.22), you would need to send the frame on the PVC that goes to me.   The PVC that goes to me is the one with your local DLCI of 33.

           

          Think of the DLCI number as a freeway on-ramp.   That is all it is.

           

          The frame map on your router would be:

           

          frame map ip 10.0.0.22 33 broadcast  (using your DLCI 33 as an onramp to reach me at 10.0.0.22)

           

          The frame map on my router would be

           

          frame map ip 10.0.0.33 22 broadcast (using my DLCI 22 as an onramp to reach you at 10.0.0.33)

           

          Best wishes,

           

          Keith

          • 2. Re: frame-relay map ip command
            Angela

            Hi, Keith,

             

              I have to say that I disagree, DLCI is only locally significant unless you are using global DLCI, which is not specified in this case. As for a local DLCI, the DLCI is how your router send and get traffic from the Frame Relay cloud. So, I agree with the answer that RouterA should have a DLCI of 100.

             

            Please correct if there is anything wrong,

             

            Regards,

            Angela

            • 3. Re: frame-relay map ip command
              Keith Barker - CCIE RS/Security, CISSP

              Hello Angela -

               

              For the CCNA level, the primary focus will be a locally signifcant DLCI, hence the analogy of the onramp. 

               

              Angela, you are right about an option in frame for a Global DLCI.

               

              Thank you,

               

               

              Keith

              • 4. Re: frame-relay map ip command
                Angela

                  I'm sorry, Keith, I thought you said the answer is wrong, that's why I said "I disagree". It turns out I wasn't fully awaken, I apologize for my careless mistake....

                 

                Regards

                • 5. Re: frame-relay map ip command
                  networkguy09

                  Sorry for the delayed response. The reason for my confusion is my Cisco book (CCNA ICND2 Official Exam Certification Guide, Second Edition) seems to contradict what the DLCI should be in this case. Pages 495-497 talk about Inverse ARP and static mapping. There is an Inverse ARP diagram given that looks like the following:

                   

                  Router Mayberry (DLCI 51) ------ Frame Relay Cloud  ------Router Mount Pilot (DLCI 52)

                   

                  <--- status DLCI 52 Up                                                status DLCI 51 Up --->

                   

                  ------------------------------------------> I-ARP I am 199.1.1.1.1 --------------------------------------------->

                   

                  <------------------------------------------ I-ARP I am  199.1.1.1.2 <---------------------------------------------

                   

                   

                  The next section on static mapping uses the above example to show a static map configuration


                  Mayberry

                  interface serial 0/0/0

                    no frame-relay inverse-arp

                    frame-relay map ip 199.1.1.2 52 broadcast



                  Mount Pilot

                  interface serial 0/0/0

                    no frame-relay  inverse-arp

                    frame-relay map ip 199.1.1.1 51 broadcast

                   

                   

                  The Mayberry router is using Mount Pilot's IP and DLCI. Am I just totally missing something here? A few other points come to mind when looking at this example and the earlier question.

                   

                  1. In the earlier question there is no "no frame-relay  inverse-arp" command. Is this command no longer needed once the frame-relay map command is used?
                  2. No IP address is shown on the book example configuration.

                   

                  Another question I have is about the Frame Relay encapsulation types: Cisco and IETF

                   

                  Are those used to determine the formatting of the LAPF? Or is RFC1490/2427 specifically IETF?

                   

                  Thanks for the help!

                  • 6. Re: frame-relay map ip command
                    Scott Morris - CCDE/4xCCIE/2xJNCIE

                    I'd say the logic is good there based on how I'm reading the diagram.

                     

                    "show frame pvc" will certainly tell us 100% on that one!

                     

                    HTH,

                     

                    Scott

                    • 7. Re: frame-relay map ip command
                      Scott Morris - CCDE/4xCCIE/2xJNCIE

                      The Mayberry router is using Mount Pilot's IP and DLCI. Am I just totally missing something here? A few other points come to mind when looking at this example and the earlier question.

                       

                      1. In the earlier question there is no "no frame-relay  inverse-arp" command. Is this command no longer needed once the frame-relay map command is used?
                      2. No IP address is shown on the book example configuration.

                       

                      Unless there's another diagram, things are a little wierd there.  But look at your first set of responses with inverse arp:

                       

                      Router Mayberry (DLCI 51) ------ Frame Relay Cloud  ------Router Mount Pilot (DLCI 52)

                       

                      <--- status DLCI 52 Up                                                status DLCI 51 Up --->

                       

                      ------------------------------------------> I-ARP I am 199.1.1.1.1 --------------------------------------------->

                       

                      <------------------------------------------ I-ARP I am  199.1.1.1.2 <---------------------------------------------

                       

                      The fact that Mayberry receives a message saying "DLCI 52 Up" tells me that 52 is really local to that side.  Which makes the first/initial line of text very confusing to interpret!  Just bad tech editing IMHO!

                       

                       

                       

                       

                      With no ip address shown on either side, it will be difficult to have pings actually work! 

                       

                       

                      Encapsulations are end to end.  So each side would choose one.  Cisco is the default method on Cisco routers (go figure).  Encapsulation is use to determine how the frames are sent.  LAPF is a control mechanism.  While it's part of the FRF standards, it is independent of the "encapsulation" used here.

                       

                       

                      HTH,

                       

                      Scott

                      • 8. Re: frame-relay map ip command
                        networkguy09

                        Okay, so your saying that 52 is really Mayberry's local DLCI? The diagram does have the FR switches inside the cloud so the status message of "DLCI 52 Up" is coming from the FR switch. For some reason I looked at that and thought it was coming all the way from the Mount Pilot router because it has DLCI 52 written just underneath it. I suppose the thinking behind this is the use DLCI 52 to go to 199.1.1.2. The pipe explination makes perfect sense too.

                        • 9. Re: frame-relay map ip command
                          Angela

                          Hi,

                           

                            Can you double check this is not a global DLCI? Global DLCI certainly means different than local DLCI. I'm absolutely sure that Wendell Odom mentioned it somewhere in his book. It has a different representation than local DLCI too.

                           

                          Regards

                          • 10. Re: frame-relay map ip command
                            networkguy09

                            How would that change anything? The book says that "global addressing is simply a way of choosing DLCI numbers when planning a Frame Relay network..." and that "because local addressing is a fact, global addressing does not change these rules..." referring to the rules of local significance

                             

                            I'm sorry to report that I am pretty confused at this point. Everything in the book is clear and makes sense to me but at the same time I don't understand why the frame-relay map ip command is one way in the book and the other way in my original question. Sure there are additional/missing commands as I pointed out that may make it impossible to compare these questions, but I don't know. Going back to Keith's PVC pipe explanation that you enter in the DLCI number on your end of the pipe along with the next hop IP address of the remote router in order to create the static map. My next question is that when Router A (with DLCI 40) sends a frame to Router B (with DLCI 41) Router A uses DLCI 41 to send the frame to Router B? But if you use static mapping you would tell Router A to use DLCI 40?

                            • 11. Re: frame-relay map ip command
                              networkguy09

                              I think the book is just confusing me. This clearly shows what everyone here has been saying.

                               

                              http://www.cisco.com/en/US/tech/tk713/tk237/technologies_tech_note09186a008014f8a7.shtml

                              • 12. Re: frame-relay map ip command
                                Keith Barker - CCIE RS/Security, CISSP

                                Hey Networkguy -

                                 

                                I know you have had a ton of great feeback on this question. 

                                 

                                Just to summarize, and put a nail in the coffin, here is a brief video that discusses it, and demonstrates it too.

                                 

                                Double click the video to make it bigger.

                                 

                                This file is available in my documents section on this forum as well.

                                 

                                Best wishes,

                                 

                                Keith

                                • 13. Re: frame-relay map ip command
                                  Angela

                                  Hello,

                                   

                                    Now I see the source of your problem, global DLCI is totally and absolutely, extremely different from local DLCI.

                                   

                                    Using Keith's example from the video above (if he doesn't mind let me use it), R1 is connected to R2 and R3 using DLCI 102 and 103 respectively, while R2 and R3 connect back using 201 and 301, respectively.

                                   

                                    Now, this topology (local DLCI) is called point-to-point topology, because there is one-to-one correspondence. If you want to reach R2 from R1, use DLCI 201 -> 201, or vice versa on the way back.

                                   

                                    Another (local DLCI) topology is called multipoint. This time, R1 has only one PVC connect to it, let's called it 101 instead. Now, even though there are ACTUALLY 2 connections, R1 can only see one PVC, that means it must use that PVC for all connections, regardless it's going to R2 or R3 (meaning DLCI 101 -> 201 and DLCI 101 -> 301), always through PVC 101, but R2 and R3 retain their thought and still believe they can reach R1 using DLCI 201 (201 ->101) and 301 (301 -> 101), respectively. This is why it's called local DLCI, it changes only the local router's configuration. R2 and R3 doesn't really care what DLCI R1 is using.

                                   

                                    On the other hand, global DLCI is a completely different matter. Let's use the old example with R1, R2, and R3. R1, let's say, now have a global DLCI of 100, R2 has 200, and R3 is 300. What this means is that to reach R1 from R2, the path is DLCI 100 (R2 side) -> 200 (R1 side). The logic is TOTALLY the opposite of local DLCI!!! This also means for R3 to reach R1, it would take DLCI 100 (R3 side) -> 300 (R1 side).

                                   

                                    Make sure you REREAD the section, it's very confusing but fun. I believe WO has a note about the difference local and global DLCI are mapped. Oh, by the way, global DLCI is not really that common in the real world, but it might appear on the exam.

                                   

                                  Regards

                                  • 14. Re: frame-relay map ip command
                                    networkguy09

                                    Thank you all again for the assistance. Great videos Keith! I'm checking them all out. Especially like the one explaining zone-based firewalls! It helped me at work to further prove communication was work between two devices! I do have a couple of questions about them though. You said the number of packets in the tcp portion of the 'show policy-map type inspect zone-pair sessions' represented the number of sessions. Is that the case for any protocol? Also regarding rate limiting, if I wanted to rate limit one server would using the zone based firewall for this purpose be the best approach? Thanks again!

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