Step 4: Monitor Statistics for a SONET Interface

Action

To monitor statistics for a SONET interface, use the following JUNOS CLI operational mode command:

user@host> monitor interface so-fpc/pic/port

   
CAUTION: We recommend that you use this command only for diagnostic purposes. Do not leave it on during normal router operations because real-time monitoring of traffic consumes additional CPU and memory resources.


 

Sample Output

user@router> monitor interface so-1/1/1

router                       Seconds: 168                 Time: 15:48:50

Interface: so-1/1/1, Enabled, Link is Down

Encapsulation: Cisco-HDLC, Keepalives, Speed: OC3

Traffic statistics:                                           Current Delta

  Input bytes:                  375527568 (0 bps)                       [0]

  Output bytes:                   6612857 (0 bps)                     [475]

  Input packets:                   224001 (0 pps)                       [0]

  Output packets:                  102090 (0 pps)                      [20]

Encapsulation statistics:

  Input keepalives:                     0                               [0]

  Output keepalives:                  176                              [17]

Error statistics:

  Input errors:                         0                               [0]

  Input drops:                          0                               [0]

  Input framing errors:               179                              [17]

  Policed discards:                    47                               [0]

  L3 incompletes:                       0                               [0]

  L2 channel errors:                    0                               [0]

  L2 mismatch timeouts:                 0                               [0]

  Carrier transitions:                  1                               [0]

  Output errors:                        0                               [0]

  Output drops:                         0                               [0]

  F2      : 0x00  Z3        : 0x00  Z4        : 0x00

Interface warnings:

  o Received keepalive count is zero

  o Framing errors are increasing, check FCS configuration and link

Next='n', Quit='q' or ESC, Freeze='f', Thaw='t', Clear='c', Interface='i'

What It Means

This output checks for and displays common interface failures, whether or not loopback is detected, and any increases in framing errors. Information from this command can help you narrow down possible causes of an interface problem.

NOTE: If you are accessing the router from the console connection, make sure you set the CLI terminal type using the set cli terminal command.

The statistics in the second column are the cumulative statistics since the last time they were cleared using the clear interfaces statistics interface-name command. The statistics in the third column are the statistics since the monitor interface interface-name command was executed.

If the framing errors are increasing, verify that the frame check sequence (FCS) and scrambling configuration match on both ends of the connection. If the configuration is correct, check the cabling to the router and have the carrier verify the integrity of the line.

If the input errors are increasing, check the cabling to the router and have the carrier verify the integrity of the line.

If you are sending output keepalives but are not receiving any input keepalives, verify that the encapsulation and keepalive configurations match on both ends of the connection.

Table 28 lists and describes the SONET error statistics in the output for the monitor interface command. The output fields are listed in the order in which they appear in the output.

Table 28: SONET Error Statistics

Output Field	Output Field Description
Input errors	Sum of the incoming frame aborts and FCS errors.
Input drops	Number of packets dropped by the output queue of the I/O Manager ASIC. If the interface is saturated, this number increments once for every packet that is dropped by the ASIC's random early detection (RED) mechanism.
Input framing errors	Sum of ATM Adaption Layers (AAL5) packets that have FCS errors, AAL5 packets that have reassembly timeout errors, and AAL5 packets that have length errors.
Policed discards	Frames that the incoming packet match code discarded because they were not recognized or of interest. Usually, this field reports protocols that the JUNOS software does not handle, such as the Cisco Discovery Protocol (CDP).
L3 incompletes	Increments when the incoming packet fails Layer 3 (usually IPv4) sanity checks of the header. For example, a frame with less than 20 bytes of available IP header would be discarded and this counter would increment.
L2 channel errors	Increments when the software cannot find a valid logical interface for an incoming frame.
L2 mismatch timeouts	Count of malformed or short packets that cause the incoming packet handler to discard the frame as unreadable.
Carrier transitions	Number of times the interface has gone from down to up. This number should not increment quickly, increasing only when the cable is unplugged, the far-end system is powered down and up, or a similar problem occurs. If it increments quickly (perhaps once every 10 seconds), then the cable, the far-end system, or the PIC is broken.
Output errors	Sum of the outgoing frame aborts and FCS errors.
Output drops	Number of packets dropped by the output queue of the I/O Manager ASIC. If the interface is saturated, this number increments once for every packet that is dropped by the ASIC's RED mechanism.