Monitor Statistics for a Fast Ethernet or Gigabit Ethernet Interface
Purpose
To monitor statistics for a Fast Ethernet or Gigabit Ethernet interface, use the following Junos OS CLI operational mode command:
Action
 | Caution: We recommend that you use the monitor interface fe-fpc/pic/port or monitor interface ge-fpc/pic/port command only for diagnostic purposes. Do not leave these commands on during normal router or switch operations because real-time monitoring of traffic consumes additional CPU and memory resources. |
Sample Output
The following sample output is for a Fast Ethernet interface:
user@host> monitor interface fe-2/1/0 Interface: fe-2/1/0, Enabled, Link is Up Encapsulation: Ethernet, Speed: 100mbps Traffic statistics: Current Delta Input bytes: 282556864218 (14208 bps) [40815] Output bytes: 42320313078 (384 bps) [890] Input packets: 739373897 (11 pps) [145] Output packets: 124798688 (1 pps) [14] Error statistics: Input errors: 0 [0] Input drops: 0 [0] Input framing errors: 0 [0] Policed discards: 6625892 [6] L3 incompletes: 75 [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 Input MAC/Filter statistics: Unicast packets 464751787 [154] Packet error count 0 [0]
Meaning
Use the information from this command to help narrow down possible causes of an interface problem.
 | Note: If you are accessing the router or switch 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 cumulative statistics since the monitor interface interface-name command was executed.
If the input errors are increasing, verify the following:
- Check the cabling to the router and have the carrier verify the integrity of the line. To verify the integrity of the cabling, make sure that you have the correct cables for the interface port. Make sure you have single-mode fiber cable for a single-mode interface and multimode fiber cable for a multimode interface.
- For a fiber-optic connection, measure the received light level at the receiver end and make sure that it is within the receiver specification of the Ethernet interface. See Fiber-Optic Ethernet Interface Specifications for the fiber-optic Ethernet interface specifications.
- Measure the transmit light level on the Tx port to verify that it is within specification. See Fiber-Optic Ethernet Interface Specifications for the optical specifications.
