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Locating the Fast Ethernet and Gigabit Ethernet LINK Alarm and Counters

 

Checklist for Locating Fast Ethernet and Gigabit Ethernet Alarms and Counters

Purpose

To locate LINK alarm and major counters associated with Fast Ethernet and Gigabit Ethernet interfaces.

Action

Table 1 provides links and commands for locating LINK alarm and major counters for Fast Ethernet and Gigabit Ethernet interfaces.

Table 1: Checklist for Locating Fast Ethernet and Gigabit Ethernet Alarms and Counters

Tasks

Command or Action

Display the Fast Ethernet or Gigabit Ethernet Interface LINK Alarm

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

Fast Ethernet and Gigabit Ethernet Counters 

Problem

Description: To display the Fast Ethernet or Gigabit Ethernet LINK alarm, use the following Junos OS command-line interface (CLI) operational mode command:

Solution

Sample Output

The following sample output is for a Fast Ethernet interface:

Meaning

The sample output shows where the alarm and other errors might be occurring and any counters that are incrementing. The only alarm associated with Fast Ethernet or Gigabit Ethernet interfaces is the LINK alarm. A LINK alarm indicates a physical problem. To isolate where the physical problem might be occurring, conduct loopback testing. See Checklist for Using Loopback Testing for Fast Ethernet and Gigabit Ethernet Interfaces for information on conducting a loopback test.

Note

Since link status is polled once every second, some items that require fast link down detection, such as Multiprotocol Label Switching (MPLS) fast reroute, take longer to execute.

Fast Ethernet and Gigabit Ethernet Counters

Problem

Description: Table 2 shows the major counters that appear in the output for the show interfaces fe-fpc/pic/port extensive and the show interfaces ge-fpc/pic/port extensive commands. These counters generally increment when there is a problem with a Fast Ethernet or Gigabit Ethernet interface. In the Counters column, the counters are listed in the order in which they are displayed in the output.

Solution

Table 2: Major Fast Ethernet and Gigabit Ethernet Counters

Counter

Description

Reason for Increment

Input Errors:

Errors

The sum of the incoming frame aborts and frame check sequence (FCS) errors.

 

Policed discards

The frames discarded by the incoming packet match code.

The frames were discarded because they were not recognized or of interest. Usually, this field reports protocols that the Junos OS does not handle.

Drops

The number of packets dropped by the output queue of the I/O Manager application-specific integrated circuit (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.

L3 incompletes

The number of packets discarded due to the packets failing Layer 3 header checks.

This counter increments when the incoming packet fails Layer 3 (usually IPv4) 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

The errors that occur when the software could not find a valid logical interface (such as fe-1/2/3.0) for an incoming frame.

This error increments when, for example, a lookup for a virtual LAN (VLAN) fails.

L2 mismatch timeouts

The count of malformed or short packets.

The malformed or short packets cause the incoming packet handler to discard the frame and be unreadable.

FIFO errors

The number of first in, first out (FIFO) errors in the receive direction as reported by the ASIC on the Physical Interface Card (PIC).

The value in this field should always be 0. If this value is not zero, cabling could be badly organized or the PIC could be broken.

Output Errors

Errors

The sum of outgoing frame aborts and FCS errors.

 

Collisions

The number of Ethernet collisions.

The Fast Ethernet PIC supports only full-duplex operation, so this number should always remain 0. If it is incrementing, there is a software bug.

Drops

The 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.

Aged packets

The number of packets that remained in shared packet SDRAM for so long that the system automatically purged them.

The value in this field should never increment. If it increments, it is probably a software bug or broken hardware.

HS link FCS errors, FIFO errors

The number of errors on the high-speed links between the ASICs responsible for handling the router interfaces.

The value in this field should always be 0. If it increments, either the FPC or the PIC is broken.

Miscellaneous Counters

Input DA rejects

The number of packets that the filter rejected because the destination Media Access Control (MAC) address of the packet is not on the accept list.

It is normal for this value to increment. When it increments very quickly and no traffic is entering the router from the far-end system, either there is a bad Address Resolution Protocol (ARP) entry on the far-end system, or multicast routing is not on and the far-end system is sending many multicast packets to the local router (which the router is rejecting).

Output packet pad count

The number of packets that the filter padded to the minimum Ethernet size (60 bytes) before giving the packet to the MAC hardware.

Usually, padding is done only on small ARP packets, but some very small Internet Protocol (IP) packets can also require padding. If this value increments rapidly, either the system is trying to find an ARP entry for a far-end system that does not exist, or it is misconfigured.

Output packet error count

Number of packets with an indicated error that the filter was given to transmit.

These packets are usually aged packets or are the result of a bandwidth problem on the FPC hardware. On a normal system, the value of this field should not increment.

CAM destination filters, CAM source filters

The number of entries in the content-addressable memory (CAM) dedicated to destination and source MAC address filters.

There can be up to 64 source entries. If source filtering is disabled, which is the default, the value for these fields should be 0.