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Monitor Fast Ethernet and Gigabit Ethernet Interfaces

SUMMARY Learn how to effectively monitor Fast Ethernet and Gigabit Ethernet interfaces by following a comprehensive checklist, understanding key monitoring techniques, and reviewing fiber-optic Ethernet interface specifications.

Checklist to Monitor Fast Ethernet and Gigabit Ethernet Interfaces

Purpose

To monitor Fast Ethernet and Gigabit Ethernet interfaces and interface problems.

Action

It provides links and commands for monitoring Fast Ethernet and Gigabit Ethernet interfaces.

Table 1: Monitor Fast Ethernet and Gigabit Ethernet Interfaces

Tasks

Command or Action

Monitor Fast Ethernet and Gigabit Ethernet Interfaces

Display the Status of Fast and Gigabit Ethernet Interfaces

show interfaces terse (fe* | ge*)

Display the Status of Specific Fast and Gigabit Ethernet Interface

show interfaces (fe-fpc/pic/port | ge-fpc/pic/port)

Display Extensive Status for a Specific Fast Ethernet or Gigabit Ethernet Interface

show interfaces (fe-fpc/pic/port | ge-fpc/pic/port) extensive

Monitor Statistics for a Fast Ethernet or Gigabit Ethernet Interface

monitor interface (fe-fpc/pic/port | ge-fpc/pic/port)

Meaning

You can use the commands to monitor and to display the configurations for Fast Ethernet and Gigabit Ethernet interfaces.

How to Monitor Fast Ethernet and Gigabit Ethernet Interfaces

Monitor the Fast Ethernet and Gigabit Ethernet interfaces to isolate interfaces related problems.

To monitor your Fast Ethernet and Gigabit Ethernet interfaces, follow these steps:

Display the Status of Fast and Gigabit Ethernet Interfaces

Purpose

To display the status of Fast and Gigabit Ethernet interfaces, use the following Junos OS command-line interface (CLI) operational mode command:

Action

Sample Output

Meaning

The sample output lists only the Fast and Gigabit Ethernet interfaces. It shows the status of both the physical and logical interfaces.

Table 2: Fast and Gigabit Ethernet Interfaces Status

Physical Interface

Logical Interface

Status Description

fe-2/1/0

Admin Up

Link Up

fe-2/1/0.0

Admin Up

Link Up

This interface has both the physical and logical links up and running.

fe-3/0/2

Admin Up

Link Down

fe-3/0/2.0

Admin Up

Link Down

This interface has the physical link down, the link layer down, or both down (Link Down). The logical link is also down as a result.

fe-4/1/0

Admin Down

Link Up

fe-4/1/0.0

Admin Up

Link Down

This interface is administratively disabled and the physical link is healthy (Link Up), but the logical interface is not established. The logical interface is down because the physical link is disabled.

fe-4/1/2

Admin Up

Link Down

fe-4/1/2.0

Admin Up

Link Down

This interface has both the physical and logical links down.

Display the Status of Gigabit Ethernet Interfaces

Purpose

To display the status of Gigabit Ethernet interfaces, use the following Junos OS command-line interface (CLI) operational mode command:

Action

Meaning

This sample output lists only the Gigabit Ethernet interfaces. It shows the status of both the physical and logical interfaces. See Table 3 for a description of what the output means.

Table 3: Status of Gigabit Ethernet Interfaces

Physical Interface

Logical Interface

Status Description

ge-2/2/0

Admin Down

Link Down

ge-2/2/0.0

Admin Up

Link Down

This interface is administratively disabled (Admin Down). Both the physical and logical links are down (Link Down).

ge-2/3/0

Admin Up

Link Up

ge-2/3/0.0

Admin Up

Link Up

This interface has both the physical and logical links up and running.

ge-3/2/0

Admin Up

Link Down

ge-3/2/0.0

Admin Up

Link Down

This interface has both the physical link and the logical interface down.

Display the Status of a Specific Fast Ethernet and Gigabit Ethernet Interface

Purpose

To investigate the status of a specific Ethernet interface, use the following CLI command to view its details:

Action

Sample Output 1

The following sample output is for a Fast Ethernet interface with the physical link up:

Sample Output 2

The following output is for a Gigabit Ethernet interface with the physical link up:

Meaning

The first line of sample output 1 and 2 shows that the physical link is up, indicating that it is healthy and can pass packets. Scroll through the output to check for any active alarms or defects. If alarms or defects are present, refer to Display Extensive Status Information for a Specific Fast Ethernet or Gigabit Ethernet Interface, for more detailed diagnostic information about the interface. 

Display Extensive Status for a Specific Fast Ethernet or Gigabit Ethernet Interface

Purpose

To display extensive status information about a specific Fast Ethernet or Gigabit Ethernet interface, use the following Junos OS CLI operational mode command:

Action

Sample Output

The following sample output is for a Fast Ethernet interface:

Meaning

The sample output shows where the errors might be occurring and includes autonegotiation information.

Table 4: Errors and their Meaning

Error

Meaning

Policed discards

Discarded frames that were not recognized or were not of interest.

L2 channel errors

Packets for which the router could not find a valid logical interface. For example, the packet is for a virtual LAN (VLAN) that is not configured on the interface.

MTU

The maximum transmission unit (MTU) must match the interface of either the router at the remote end of the Fast Ethernet or Gigabit Ethernet link, or that of the switch.

Input DA rejects

Number of packets with a destination Media Access Control (MAC) address that is not on the accept list. It is normal to see this number increment.

Input SA rejects

Number of packets with a source MAC address that is not on the accept list. This number only increments when source MAC address filtering is configured.

If the physical link is down, look at the active alarms and defects for the Fast Ethernet or Gigabit Ethernet interface and diagnose the Fast Ethernet or Gigabit Ethernet media accordingly. See Locate LINK Alarms and Counters for Fast and Gigabit Ethernet for an explanation of Fast Ethernet and Gigabit Ethernet alarms.

Table 5: MAC Statistics Errors

Error

Meaning

CRC/Align errors

The total number of packets received that had a length (excluding framing bits, but including FCS octets) of between 64 and 1518 octets, inclusive, but had either a bad FCS with an integral number of octets (FCS Error) or a bad FCS with a non-integral number of octets (Alignment Error).

MAC control frames

The number of MAC control frames.

MAC pause frames

The number of MAC control frames with pause operational code.

Jabber frames

The total number of packets received that were longer than 1518 octets (excluding framing bits, but including FCS octets), and had either an FCS error or an alignment error.

Note that this definition of jabber is different from the definition in IEEE-802.3 section 8.2.1.5 (10BASE5) and section 10.3.1.4 (10BASE2). These documents define jabber as the condition where any packet exceeds 20 ms. The allowed range to detect jabber is between 20 ms and 150 ms.

Fragment frames

The total number of packets received that were less than 64 octets in length (excluding framing bits, but including FCS octets), and had either an FCS error an alignment error.

Note that it is entirely normal for fragment frames to increment because both runts (which are normal occurrences due to collisions) and noise hits are counted.

Autonegotiation is the process that connected Ethernet interfaces use to communicate the information necessary to interoperate. Table 6 explains the autonegotiation information of the show interface interface-name extensive command output.

Table 6: Autonegotiation Field Information

Autonegotiation Field Information

Explanation

Negotiation status: Incomplete

Ethernet interface has the speed or link mode configured.

Negotiation status: No autonegotiation

Ethernet interface has the speed or link mode configured, or does not perform autonegotiation.

Negotiation status: Complete Link partner status: OK

Ethernet interface is connected to a device that performs autonegotiation and the autonegotiation process completes successfully.

Link partner: Half-duplex

Depends on the capability of the attached Ethernet device.

Flow control: Symmetric/asymmetric

Displays the types of flow control supported by the remote Ethernet device.

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

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 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:

Meaning

Use the information from this command to help narrow down possible causes of an interface problem.

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 second column shows cumulative statistics since the last time you cleared them using the clear interfaces statistics interface-name command. The third column shows cumulative statistics since you ran the monitor interface interface-name command. If input errors are increasing, follow these steps:

  • Check the cabling to the router and ask the carrier to verify the line’s integrity. Ensure you are using the correct cables for the interface port—single-mode fiber for a single-mode interface, and multimode fiber for a multimode interface.

  • For fiber-optic connections, measure the received light level at the receiver end and ensure it meets the Ethernet interface’s specification.

  • Measure the transmit light level on the Tx port to confirm it is within the specified range.

Fiber-Optic Ethernet Interface Specifications

Table 7 shows the specifications for fiber-optic interfaces.

Table 7: Fiber-Optic Ethernet Interface Specifications

Fiber-Optic Ethernet Interface

Length

Wavelength

Average Launch Power

Receiver Saturation

Receiver Sensitivity

Gigabit Ethernet

Duplex SC connector

 

LH optical interface

49.5-mile 70-km reach on 8.2-micrometer SMF

1480 to 1580 nm

-3 to +2 dBm

-3 dBm

-23 dBm (BER 1012) for SMF

LX optical interface

6.2-mile 10-km reach on 9/125-micrometer SMF

1804.5-ft 550-m reach on 62.5/125- and 50/125-micrometer MMF

1270 to 1355 nm

-11 to -3 dBm

-3 dBm

-19 dBm

SX optical interface

656-ft 200-m reach on 62.5/125-micrometer MMF

1640-ft 500-m reach on 50/125-micrometer MMF

830 to 860 nm

-9.5 to -4 dBm

-3 dBm

-17 dBm

Fast Ethernet 8-Port

FX optical interface with MT-RJ connector

1.24-mile 2-km reach on 62.5/125-micrometer MMF

1270 to 1380 nm

-20 to -14 dBm

-14 dBm

-34 dBm