LAPB configuration example

As shown in Figure 135, run IP on the interfaces to transmit IP datagrams.

1. Configure Router A:

   # Enter interface view.

   <RouterA> system-view
   [RouterA] interface serial 2/0
   

   # Assign an IP address for the interface.

   [RouterA-Serial2/0] ip address 10.1.1.2 255.0.0.0
   

   # Configure the link layer protocol of the interface as LAPB, and specify it to operate in DTE mode.

   [RouterA -Serial2/0] link-protocol lapb dte
   

   # Configure other LAPB parameters.

   [RouterA-Serial2/0] lapb modulo 128
   [RouterA-Serial2/0] lapb window-size 127
   [RouterA-Serial2/0] shutdown
   [RouterA-Serial2/0] undo shutdown
   

2. Configure Router B:

   # Enter interface view.

   <RouterB> system-view
   [RouterB] interface serial 2/0
   

   # Assign an IP address for the interface.

   [RouterB-Serial2/0] ip address 10.1.1.1 255.0.0.0
   

   # Configure the link layer protocol of the interface as LAPB, and specify it to operate in DCE mode.

   [RouterB-Serial2/0] link-protocol lapb dce
   

   # Configure other LAPB parameters.

   [RouterB-Serial2/0] lapb modulo 128
   [RouterB-Serial2/0] lapb window-size 127
   [RouterB-Serial2/0] shutdown
   [RouterB-Serial2/0] undo shutdown
   

   The IP addresses of the two connected interfaces must be on the same network segment. If they are not on the same network segment, configure a static route in between and make sure the traffic control parameters of both sides are the same.

# Display information about interface Serial 2/0 on Router A.

[RouterA-Serial2/0] display interface serial 2/0
Serial2/0 current state: UP
Line protocol current state: UP
Description: Serial2/0 Interface
The Maximum Transmit Unit is 1500, Hold timer is 10(sec)
Internet Address is 10.1.1.2/8 Primary
Link-protocol is LAPB
  LAPB DTE, module 128, window-size 127, max-frame 12032, retry 10
  Timer:  T1 3000, T2 1500, T3 0 , T4 0 (milliseconds),  IP-protocol
  state CONNECT, VS 6, VR 0, Remote VR 6
  IFRAME 0/6, RR 6/0, RNR 0/0, REJ 0/0
  FRMR 0/1, SABM 3/19, DM 0/1, UA 0/1
  DISC 0/0, invalid ns 0, invalid nr 0, link resets 0
Output queue : (Urgent queuing : Size/Length/Discards)  0/100/0
Output queue : (Protocol queuing : Size/Length/Discards)  0/500/0
Output queue : (FIFO queuing : Size/Length/Discards)  0/75/0
Physical layer is synchronous, Virtual baudrate is 64000 bps
Interface is DTE, Cable type is V24, Clock mode is DTECLK1
Last clearing of counters: Never
    Last 300 seconds input rate 2.26 bytes/sec, 18 bits/sec, 0.19 packets/sec
    Last 300 seconds output rate 2.54 bytes/sec, 20 bits/sec, 0.22 packets/sec
    Input: 627 packets, 7462 bytes
           0 broadcasts, 0 multicasts
           0 errors, 0 runts, 0 giants
           0 CRC, 0 align errors, 0 overruns
           0 dribbles, 0 aborts, 0 no buffers
           0 frame errors
    Output:633 packets, 7737 bytes
           0 errors, 0 underruns, 0 collisions
           0 deferred
    DCD=UP  DTR=UP  DSR=UP  RTS=UP  CTS=UP

# Display information about interface Serial 2/0 on Router B.

[RouterB-Serial2/0] display interface serial 2/0
Serial2/0 current state: UP
Line protocol current state: UP
Description: Serial2/0 Interface
The Maximum Transmit Unit is 1500, Hold timer is 10(sec)
Internet Address is 10.1.1.1/8 Primary
Link-protocol is LAPB
  LAPB DCE, module 128, window-size 127, max-frame 12032, retry 10
  Timer:  T1 3000, T2 1500, T3 0 , T4 0 (milliseconds),  IP-protocol
  state CONNECT, VS 66, VR 112, Remote VR 66
  IFRAME 240/194, RR 1/44, RNR 0/0, REJ 0/0
  FRMR 1/0, SABM 0/3, DM 1/0, UA 1/0
  DISC 0/0, invalid ns 0, invalid nr 0, link resets 1
Output queue : (Urgent queuing : Size/Length/Discards)  0/100/0
Output queue : (Protocol queuing : Size/Length/Discards)  0/500/0
Output queue : (FIFO queuing : Size/Length/Discards)  0/75/0
Physical layer is synchronous, Baudrate is 64000 bps
Interface is DCE, Cable type is V24, Clock mode is DCECLK
Last clearing of counters: Never
    Last 70 seconds input rate 6.69 bytes/sec, 53 bits/sec, 0.10 packets/sec
    Last 70 seconds output rate 0.30 bytes/sec, 2 bits/sec, 0.10 packets/sec
    Input: 865 packets, 20440 bytes
           0 broadcasts, 0 multicasts
           0 errors, 0 runts, 0 giants
           0 CRC, 0 align errors, 0 overruns
           0 dribbles, 0 aborts, 0 no buffers
           0 frame errors
    Output:861 packets, 17678 bytes
           0 errors, 0 underruns, 0 collisions
           0 deferred
    DCD=UP  DTR=UP  DSR=UP  RTS=UP  CTS=UP