14 Replies Latest reply: Jan 20, 2018 5:30 PM by ProgSnob RSS

    T1 Configured Properly?

    Derpy

      I have two 1841 routers with HWIC-1DSU T1 cards. I also purchased T1 crossover cables. Everything work just fine. Since both cards and routers are identical, I can get away with the defaults as you can see below with my show run output. My question is both sides default to "line". Isn't one side supposed to be "line" and the other "internal"? I looked it up but line vs internal is confusing.

       

       

      Router#show run | b Serial0/0/0

      interface Serial0/0/0

      ip address 192.168.0.1 255.255.255.0

      no fair-queue

      !

       

      Router#show ip int br | i Serial0/0/0

      Serial0/0/0                192.168.0.1     YES manual up                    up

       

      Router#show int s0/0/0

      Serial0/0/0 is up, line protocol is up

        Hardware is GT96K with integrated T1 CSU/DSU

        Internet address is 192.168.0.1/24

        MTU 1500 bytes, BW 1544 Kbit/sec, DLY 20000 usec,

           reliability 255/255, txload 1/255, rxload 1/255

        Encapsulation HDLC, loopback not set

        Keepalive set (10 sec)

        Last input 00:00:00, output 00:00:01, output hang never

        Last clearing of "show interface" counters 00:13:49

        Input queue: 0/75/0/0 (size/max/drops/flushes); Total output drops: 0

        Queueing strategy: fifo

        Output queue: 0/40 (size/max)

        5 minute input rate 0 bits/sec, 0 packets/sec

        5 minute output rate 0 bits/sec, 0 packets/sec

           92 packets input, 7466 bytes, 0 no buffer

           Received 87 broadcasts (0 IP multicasts)

           0 runts, 0 giants, 0 throttles

           0 input errors, 0 CRC, 0 frame, 0 overrun, 0 ignored, 0 abort

           92 packets output, 6536 bytes, 0 underruns

           0 output errors, 0 collisions, 2 interface resets

           0 unknown protocol drops

           0 output buffer failures, 0 output buffers swapped out

           1 carrier transitions

           DCD=up  DSR=up  DTR=up  RTS=up  CTS=up

       

      Router#show service-module

      Interface Serial0/0/0

      Module type is T1/fractional

          Hardware revision is 1.0, Software revision is 001,

          Image checksum is 0x8B5FDE, Protocol revision is 0.1

      Receiver has no alarms.

      Framing is ESF, Line Code is B8ZS, Current clock source is line,

      Fraction has 24 timeslots (64 Kbits/sec each), Net bandwidth is 1536 Kbits/sec.

        • 1. Re: T1 Configured Properly?
          ciscodaze1

          Yes, when there is no provider doing the clocking, then one side needs to be set as the master, using the command clock source internal, and the other side will be line (slave)...by default.

           

          Verify with show run, and show controllers T1


          Cisco IOS Interface and Hardware Component Command Reference - clock rate through cut-through [Support] - Cisco

          • 2. Re: T1 Configured Properly?
            DavidJ

            Kev gave you the answer to your question.  To add from my experience it's a good thing if you are going to work with a lot of T1 circuits is to have a line tester and a T1 loopback and crossover adapter.

              I've installed and took care of more than 100 T1 home-office/small site locations and just the delivery of the circuit can be screwed up.

             

            At the DEMARK Location:

            1.  Are the wires punched down properly?  There will be four wires on both sides with "bridge clips" to connect the two sides.  Get down to eye level to make sure pins 5-8 don't have bridge clips from 6-9.

            2.  The circuit is delivered so that you need a crossover cable to connect your DTE side to their DCE.

                 A:  I've seen them deliver a strait through so when you put in a cross over it didn't work.

                 B:  I've also seen where the T1 circuit is delivered properly as a crossover and someone extends it from the demark to the closet where the T1 is located with another crossover effectively making it a straight through.

            3.  The pinout may be punched down in the wrong order.  "Cable Tester"

             

              It's easy to screw the wiring up when the circuit is delivered.  Knowing how to troubleshoot and having the tools to figure out the problem will help you succeed.

            • 3. Re: T1 Configured Properly?
              Derpy

              My question is how does this work when both sides are set to line? If both cards are waiting for an external clock source, how does it work? Where is the clock?

               

              R1#show controllers t1

              No Output


              R2#show controllers t1

              No Output

               

              R1#show run

              interface Serial0/0/0

              ip address 192.168.0.2 255.255.255.0

              no fair-queue

               

              R2#show run

              interface Serial0/0/0

              ip address 192.168.0.1 255.255.255.0

              no fair-queue

              !

               

               

              R1#show service-module

              Interface Serial0/0/0

              Module type is T1/fractional

                  Hardware revision is 1.0, Software revision is 001,

                  Image checksum is 0x8B5FDE, Protocol revision is 0.1

              Receiver has no alarms.

              Framing is ESF, Line Code is B8ZS, Current clock source is line,

              Fraction has 24 timeslots (64 Kbits/sec each), Net bandwidth is 1536 Kbits/sec.

               

               

              R2#show service-module

              Interface Serial0/0/0

              Module type is T1/fractional

                  Hardware revision is 1.0, Software revision is 001,

                  Image checksum is 0x8B5FDE, Protocol revision is 0.1

              Receiver has no alarms.

              Framing is ESF, Line Code is B8ZS, Current clock source is line,

              Fraction has 24 timeslots (64 Kbits/sec each), Net bandwidth is 1536 Kbits/sec.

               

              -----------------------------------------------------------------------------------------------------------------------------

              Testing

               

              R2#ping 192.168.0.2

               

               

              Type escape sequence to abort.

              Sending 5, 100-byte ICMP Echos to 192.168.0.2, timeout is 2 seconds:

              !!!!!

              Success rate is 100 percent (5/5), round-trip min/avg/max = 1/3/4 ms

              • 4. Re: T1 Configured Properly?
                ciscodaze1

                (Sorry, I missed your essential question in your first post, my bad).

                 

                This seems to be one of Davids specialties, maybe he knows.

                 

                I found this on another forum: "You cannot use an internal clock source at both ends - configure one to be internal and the other to line, otherwise you will get clock slip errors."

                 

                So maybe if you set both to line, as you did, it works, but in a sort of dysfunctional way...just guessing here.

                 

                Do an extended ping repeating 3000 times with a large datagram size and see what happens.

                • 5. Re: T1 Configured Properly?
                  Derpy

                  I don't think it should work in theory because both are set to line, but it works for some reason.Why? XD

                   

                  --------------------------------------------------------------------------

                   

                  R1#ping

                  Protocol [ip]:

                  Target IP address: 192.168.0.1

                  Repeat count [5]: 3000

                  Datagram size [100]: 1500

                  Timeout in seconds [2]:

                  Extended commands [n]:

                  Sweep range of sizes [n]:

                  Type escape sequence to abort.

                  Sending 3000, 1500-byte ICMP Echos to 192.168.0.1, timeout is 2 seconds:

                  !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

                  !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

                  !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

                  !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

                  !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

                  !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

                  !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

                  !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

                  !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

                  !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

                  !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

                  !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

                  !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

                  !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

                  !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

                  !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

                  !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

                  !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

                  !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

                  !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

                  !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

                  !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

                  !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

                  !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

                  !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

                  !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

                  !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

                  !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

                  !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

                  !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

                  !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

                  !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

                  !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

                  !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

                  !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

                  !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

                  !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

                  !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

                  !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

                  !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

                  !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

                  !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

                  !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

                  Success rate is 100 percent (3000/3000), round-trip min/avg/max = 16/17/48 ms

                  R1#

                  • 6. Re: T1 Configured Properly?
                    ciscodaze1

                    don't know...we are in need of expertise here.

                     

                    the answer may simply be that it will work with the internal/internal combo, or the line/line combo, but sub-optimally, hence, the reason for the master/slave relationship...to optimize the line.

                     

                    in the meantime, take a lot at this (the last two posts at the bottom).

                    Solved: Configuring WIC-1DSU-T1-V2 on back to b... - Cisco Support Community

                     

                    try the show interface and see if you are getting crc errors, as suggested.

                    • 7. Re: T1 Configured Properly?
                      arteq

                      you posted sh controllers with no ouptut

                       

                      was "no output" your output?

                       

                      my guess is you are using default hdlc versus ppp?

                      • 8. Re: T1 Configured Properly?
                        arteq

                        my bust... i just saw it...

                         

                        Encapsulation HDLC


                        have you tried ppp

                        • 9. Re: T1 Configured Properly?
                          ProgSnob

                          I work with a lot of T1s at my job. The most common inconsistency I find is that each tech places the crossover at a different location. It creates confusion and becomes a guessing game.

                           

                          I've also seen many punch-downs completed one wire off where it's supposed to be. Like you said, viewing it at eye level is a must.

                          • 10. Re: T1 Configured Properly?
                            Derpy

                            No CRC errors. Man, this really bugs me. Why does this setup even work? Both sides can't be set to line, but it works somehow. Maybe I'll let it run for a while and see if I eventually get CRC errors. @KEV Thanks for the posts.



                            Router(config-if)#do show int s0/0/0

                            Serial0/0/0 is up, line protocol is up

                              Hardware is GT96K with integrated T1 CSU/DSU

                              Internet address is 192.168.0.2/24

                              MTU 1500 bytes, BW 1544 Kbit/sec, DLY 20000 usec,

                                 reliability 255/255, txload 70/255, rxload 70/255

                              Encapsulation HDLC, loopback not set

                              Keepalive set (10 sec)

                              Last input 00:00:00, output 00:00:00, output hang never

                              Last clearing of "show interface" counters 00:34:17

                              Input queue: 0/75/0/0 (size/max/drops/flushes); Total output drops: 0

                              Queueing strategy: fifo

                              Output queue: 0/40 (size/max)

                              5 minute input rate 426000 bits/sec, 47 packets/sec

                              5 minute output rate 427000 bits/sec, 47 packets/sec

                                 16643 packets input, 24683713 bytes, 0 no buffer

                                 Received 237 broadcasts (0 IP multicasts)

                                 0 runts, 0 giants, 0 throttles

                                0 input errors, 0 CRC, 0 frame, 0 overrun, 0 ignored, 0 abort

                                 16642 packets output, 24683391 bytes, 0 underruns

                                 0 output errors, 0 collisions, 2 interface resets

                                 3 unknown protocol drops

                                 0 output buffer failures, 0 output buffers swapped out

                                 1 carrier transitions

                                 DCD=up  DSR=up  DTR=up  RTS=up  CTS=up

                            • 11. Re: T1 Configured Properly?
                              ProgSnob

                              I was looking into the configuration using line on both ends. According to Network Warrior, leaving both ends to the default of line will work in some environments. It doesn't give specifics.

                               

                              "Internal means that the CSU/DSU will provide the clocking (master), and line indicates that the clocking will be determined from the data stream on the line(slave). The default behavior is to use the line for clocking"

                              • 12. Re: T1 Configured Properly?
                                Derpy

                                Thanks @ProgSnob and @kev! This must not be a really researched topic. I did find another blog post about it. You must be right @kev. It may work for a while then all of a sudden drop. clock source internal | Seek4UDP

                                 

                                Thanks for referencing the book! I was eyeing that for a while. Maybe I'll purchase a copy. @ProgSnob

                                 

                                I don't know about you guys, but I usually never have the problem of "why doesn't this work." I always get the "why on earth is this working?" XD

                                • 13. Re: T1 Configured Properly?
                                  ciscodaze1

                                  You can read NW for free on google books, but it is a nice book to have on your desk to just randomly pick up and start reading...more like and encyclopedia than a book.

                                   

                                  https://books.google.com/books?id=6CqQgz8r4GsC&printsec=frontcover&dq=network+warrior&hl=en&sa=X&ved=0ahUKEwjznuCU2efYAh…

                                  • 14. Re: T1 Configured Properly?
                                    ProgSnob

                                    I bought Network Warrior a few years back and it has been exceedingly helpful with my work. It delves deeper into the CCNA topics and that depth into the topics is something useful if you ever want to get your CCIE (which is what I'm studying for now). Solidifying that foundation is exceedingly beneficial.