Step 2: Verify That the Fast Ethernet or Gigabit Ethernet Interface Is Up

Purpose

Display the status of the Fast Ethernet or Gigabit Ethernet interface to provide the information you need to determine whether the physical link is up or down.

Action

To verify that the status of the Fast Ethernet or Gigabit Ethernet interface is up, use the following JUNOS command-line interface (CLI) operational mode command:

user@host> show interfaces (fe-fpc/pic/port | ge-fpc/pic/port)

Sample Output

user@host# show interfaces fe-1/3/0

Physical interface: fe-1/3/0, Enabled, Physical link is Up

  Interface index: 44, SNMP ifIndex: 35

  Link-level type: Ethernet, MTU: 1514, Source filtering: Disabled

  Speed: 100mbps, Loopback: Disabled, Flow control: Enabled

  Device flags   : Present Running

  Interface flags: SNMP-Traps

  Link flags     : None

  Current address: 00:90:69:8d:2c:db, Hardware address: 00:90:69:8d:2c:db

  Input rate     : 0 bps (0 pps), Output rate: 0 bps (0 pps)

  Active alarms  : None

  Active defects : None

  MAC statistics:

    Input octets: 0, Input packets: 0, Output octets: 0, Output packets: 0

  Filter statistics:

    Filtered packets: 0, Padded packets: 0, Output packet errors: 0

  Autonegotiation information:

    Negotiation status: Incomplete, Link partner status: OK

    Link partner: Full-duplex, Flow control: None

What It Means

The sample output shows that the link is up and there are no alarms in this loopback configuration. When an internal loopback is configured, the physical loopback should come up without an alarm.

Sample Output

When you see that the physical link is down, there may be a problem with the port. The following output is an example of the show interfaces fe-fpc/pic/port command when the physical link is down:

user@router> show interfaces fe-1/3/0

Physical interface: fe-1/3/0, Enabled, Physical link is Down

  Interface index: 44, SNMP ifIndex: 35

  Link-level type: Ethernet, MTU: 1514, Source filtering: Disabled

  Speed: 100mbps, Loopback: Disabled, Flow control: Enabled

  Device flags   : Present Running Down

  Interface flags: Hardware-Down SNMP-Traps

  Link flags     : None

  Current address: 00:90:69:8d:2c:db, Hardware address: 00:90:69:8d:2c:db

  Input rate     : 0 bps (0 pps), Output rate: 0 bps (0 pps)

  Active alarms  : LINK

  Active defects : LINK

  MAC statistics:

    Input octets: 0, Input packets: 0, Output octets: 0, Output packets: 0

  Filter statistics:

    Filtered packets: 0, Padded packets: 0, Output packet errors: 0

  Autonegotiation information:

    Negotiation status: Incomplete, Link partner status: Down

    Reason: Link partner autonegotiation failure

    Link partner: Half-duplex, Flow control: None

What It Means

The sample output shows that the physical link is down and there are active alarms and defects.

Table 44 presents problem situations and actions for a physical link that is down.

Table 44: Problems and Solutions for a Physical Link That Is Down

Problem	Action
Cable mismatch	Verify that the fiber connection is correct.
Damaged and/or dirty cable	Verify that the fiber can successfully loop a known good port of the same type.
Too much or too little optical attenuation	Verify that the attenuation is correct per the PIC optical specifications.
The transmit port is not transmitting within the dBm optical range per the specifications	Verify that the Tx power of the optics is within range of the PIC optical specification.
Mismatch between the cable type and the port	Verify that a single-mode fiber cable is connected to a single-mode interface and that a multimode fiber cable is connected to a multimode interface. (This problem does not always cause the physical link to go down; errors and dropped packets are sometimes the result.)