Serial interface "Line Protocol" up/ down question

Discussion in 'Cisco' started by PPrash, Aug 9, 2005.

  1. PPrash

    PPrash Guest

    I have multiple remote routers with the same type of ISDN backu
    setup. I have one that will not go UP, UP when doing a Show Int. Wha
    dictates if Line Protocol is UP? (See Sh Int below

    #sh int s4/
    Serial4/0 is up, line protocol is dow
    Hardware is cxBus Seria
    Internet address is
    MTU 1500 bytes, BW 64 Kbit, DLY 20000 usec
    reliability 255/255, txload 1/255, rxload 1/25
    Encapsulation PPP, crc 16, loopback not se
    Keepalive set (10 sec
    Restart-Delay is 0 sec
    LCP Close
    Closed: IPCP, CDPC
    Last input 00:00:08, output 18:55:50, output hang neve
    Last clearing of "show interface" counters 22w3
    Input queue: 0/75/0/0 (size/max/drops/flushes); Total output drops

    Queueing strategy: weighted fai
    Output queue: 0/1000/64/0 (size/max total/threshold/drops
    Conversations 0/1/256 (active/max active/max total
    Reserved Conversations 0/0 (allocated/max allocated
    Available Bandwidth 48 kilobits/se
    5 minute input rate 0 bits/sec, 0 packets/se
    5 minute output rate 0 bits/sec, 0 packets/se
    2322 packets input, 53834 bytes, 0 no buffe
    Received 0 broadcasts, 0 runts, 0 giants, 0 throttle
    0 input errors, 0 CRC, 0 frame, 0 overrun, 0 ignored, 0 abor
    1856 packets output, 38512 bytes, 0 underrun
    0 output errors, 0 collisions, 500 interface reset
    0 output buffer failures, 0 output buffers swapped ou
    4 carrier transition
    RTS up, CTS up, DTR up, DCD up, DSR u
    PPrash, Aug 9, 2005
    1. Advertisements

  2. you have configured "PPP" as the upper protocol (encapsulation) for the
    serial link and this wents from DOWN to UP only when the PPP-negotiation
    between your router and the remote one was successful. maybe the remote
    router was not configured for PPP? the default is HDLC, e.g. when
    "encapsulation" is omitted completely.

    shut/no shut together with "debug ppp ..." may help also.

    Gerald Krause, Aug 9, 2005
    1. Advertisements

  3. maybe an IP subnet mismatch?

    Andre Janssen, Aug 10, 2005
  4. PPrash

    jefflin.choi Guest

    cannot be an ip subnet mismatch because the problem is layer 2.

    as you can see in the show interface...
    "LCP Closed"
    if ever the ppp negotiation went fine, this should be LCP open.
    jefflin.choi, Aug 11, 2005
  5. I think that it is a simple line problem ,
    Or on the sending link , so you don't see any error o crc , but the
    troble exist .
    Or in a layer 2 not directly connect at your interface .

    Try to open a ticket at you carrier .

    See :

    500 interface resets

    Best Regards

    [email protected], Aug 12, 2005
  6. PPrash

    Chris Marva Guest

    generally, interface up/down refers to carrier detect, and line proto
    refers to keepalive state. Since interface is up, but line proto down,
    checking the encaps would be a good start.

    Chris Marva, Aug 12, 2005
  7. PPrash

    dbn58 Guest

    I would recommend to check if the encapsulation is the same on both sides.
    See comments below.
    Is PPP used on both sides? For serial interfaces, the default is HDLC!
    Both sides sent a lot of packets for initialization, but do not understand
    each other at all. There were no errors counted since weeks. So, L1 seems
    o.k., but L2 is not. You should check the encapsulation settings on both
    dbn58, Aug 13, 2005
  8. PPrash


    Jun 19, 2009
    Likes Received:
    Last edited: Apr 17, 2010
    theapplebee, Oct 30, 2009
    1. Advertisements

Ask a Question

Want to reply to this thread or ask your own question?

You'll need to choose a username for the site, which only take a couple of moments (here). After that, you can post your question and our members will help you out.