Display Real-Time Statistics about a Physical Interface

Purpose

Displaying real-time statistics about a physical interface is useful when you need to narrow down possible causes of an interface problem. The monitor command checks for and displays common interface failures, indicates whether loopback is detected, and shows any increases in framing errors.

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.

Action

To display real-time statistics about a physical interface, use the following Junos OS CLI operational mode command:

user@host> monitor interface interface-name

Sample Output

user@host> monitor interface so-0/0/0

router1                           Seconds: 19                  Time: 15:46:29
Interface: so-0/0/0, Enabled, Link is Up
Encapsulation: PPP, Keepalives, Speed: OC48
Traffic statistics:                                           Current Delta
  Input packets:                      6045 (0 pps)                     [11]
  Input bytes:                     6290065 (0 bps)                  [13882]
  Output packets:                    10376 (0 pps)                     [10]
  Output bytes:                   10365540 (0 bps)                   [9418]
Encapsulation statistics:
  Input keepalives:                   1901                              [2]
  Output keepalives:                  1901                              [2] 
  NCP state: Opened
  LCP state: Opened
Error statistics:
  Input errors:                          0                              [0]
  Input drops:                           0                              [0]
  Input framing errors:                  0                              [0]
  Policed discards:                      0                              [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]
  Aged packets:                          0                              [0]
Active alarms : None
Active defects: None
SONET error counts/seconds:
  LOS count                              1                              [0]
  LOF count                              1                              [0]
  SEF count                              1                              [0]
  ES-S                                   0                              [0]
  SES-S                                  0                              [0]
SONET statistics:
  BIP-B1                            458871                              [0]
  BIP-B2                            460072                              [0]
  REI-L                             465610                              [0]
  BIP-B3                            458978                              [0]
  REI-P                             458773                              [0]
Received SONET overhead:
  F1      : 0x00  J0        : 0x00  K1        : 0x00
  K2      : 0x00  S1        : 0x00  C2        : 0x00
  C2(cmp) : 0x00  F2        : 0x00  Z3        : 0x00
  Z4      : 0x00  S1(cmp)   : 0x00
Transmitted SONET overhead:
  F1      : 0x00  J0        : 0x01  K1        : 0x00
  K2      : 0x00  S1        : 0x00  C2        : 0xcf
  F2      : 0x00  Z3        : 0x00  Z4        : 0x00
Next='n', Quit='q' or ESC, Freeze='f', Thaw='t', Clear='c', Interface='i'

Meaning

The sample output displays real-time statistics about the physical interface (updating them every second), the amount that each field has changed since you started the command or since you cleared the counters by using the C key. It also checks for and displays common interface failures, such as SONET/SDH and T3 alarms, detected loopbacks, and increases in framing errors.

To control the output of the command while it is running, use the keys shown in Table 24.

Table 24: Monitor Interface Output Control Keys

Key	Action
N	Display information about the next interface. The monitor interface command scrolls through the physical or logical interfaces in the same order that they are displayed by the show interfaces terse command.
I	Display information about a different interface. The command prompts you for the name of a specific interface.
F	Freeze the display, halting the display of updated statistics.
T	Thaw the display, resuming the display of updated statistics.
C	Clear (zero) the current delta counters since monitor interface was started. It does not clear the cumulative counter.
Q	Stop the monitor interface command.