Contents

Introduction

SNMP Counters Questions

Q. Which MIB do I use for interface counters?

Q. When do 64-bit counters be used?

Q. Which version of SNMP is required to query 64-bit counters?

Q. Which Cisco devices implement 64-bit SNMP counters, especially for the IF-MIB?

Q. Are ifInOctets and ifOutOctets SNMP counters the same as the show interfaces In/Out counters?

Q. Do the ifInOctets and ifOutOctets counters include framing overhead (Point-to-Point Protocol, High-Level Data Link Control)?

Q. On an Asynchronous Transfer Mode interface, do the counters include the cell header?

Q. Why do SNMP counters not return the same number as CLIshowcommands?

SNMP Counters and show Command Equivalent Questions

Q. What do Cisco routers do for these SNMP MIB variables: ifInOctets, ifInUcastPkts, ifInNUcastPkts, ifInDiscards, ifInErrors, ifInUnknownProtos, ifOutOctets, ifOutUcastPkts, ifOutNUcastPkts, ifOutDiscards, ifOutErrors, and ifOutQLen?

Examples

Q. What is the relationship between theshow interfacesstatementsno buffersandinput queue drops? Why do the inDiscards of SNMP giveno bufferscounts and notinput queue drops, while the outDiscards of SNMP do giveoutput queue drops?

Q. Can I poll no buffers on a router?

Q. How do I poll queue limit drops on a router?

Related Information

Introduction

This document describes answers to commonly asked questions about SNMP counters as they relate to Cisco equipment.

SNMP Counters Questions

Note: Only registered Cisco users can access internal Cisco tools and information.

Q. Which MIB do I use for interface counters?

A.Interface management over SNMP is based on two tables:ifTable  and its extension, ifXTable described in RFC1213/RFC2233. Interfaces can have several layers, which depends on the media, and each sub-layer is represented by a separate row in the table. The relationship between the higher layer and lower layers is described in the ifStackTable. The ifTable defines 32-bit counters for inbound and outbound octets  (ifInOctets /ifOutOctets), packets  (ifInUcastPkts/ifOutUcastPkts) , ifInNUcastPkts /ifOutNUcastPkts, errors, and discards. The ifXTable provides imilar 64-bit counters, also called high capacity (HC) counters: ifHCInOctets/ ifHCOutOctets and ifHCInUcastPkts / ifHCOutUcastPkts.

Q. When do 64-bit counters be used?

A. RFC 2233  adopted expanded 64-bit counters for high capacity interfaces in which 32-bit counters do not provide enough capacity and wrap too fast.

As the speed of network media increases, the minimum time in which a 32-bit counter wraps decreases. For example, a 10 Mbps stream of back-to-back, full-size packets causes ifInOctets to wrap in just over 57 minutes. At 100 Mbps, the minimum wrap time is 5.7 minutes, and at 1 Gbps, the minimum is 34 seconds.

Note: The SNMP counters wrap, the command line interface (CLI) counters do not.

For interfaces that operate at 20,000,000 (20 million) bits per second or less, you must use 32-bit byte and packet counters. For interfaces that operate faster than 20 million bits per second, and slower than 650,000,000 bits per second, you must use 32-bit packet counters and 64-bit octet counters. For interfaces that operate at 650,000,000 bits/second or faster, 64-bit packet and octet counters must be used.

Correspondingly, Cisco IOS® Software does not support 64-bit counters for interface speeds of less than 20 Mbps. This means that 64-bit counters are not supported on 10 Mb Ethernet ports, only 100 Mb Fast-Ethernet and other high speed ports support 64-bit counters.

Q. Which version of SNMP is required to query 64-bit counters?

A.SNMPv2C or SNMPv3 is required to query 64-bit counters. SNMPv1 does not support 64-bit counters. Be aware that ifInOctets = .1.3.6.1.2.1.2.2.1.10 is a 32-bit counter while the 64-bit version is ifHCInOctets = .1.3.6.1.2.1.31.1.1.1.6.

For example:

Catalyst 5000 uses HP OpenView snmpget, which defaults to SNMPv1

# snmpget -c public 10.32.5.18 ifName.1

ifMIB.ifMIBObjects.ifXTable.ifXEntry.ifName.1 DISPLAY STRING- (ascii) sc0

Query with SNMPv1, default for HP OpenView snmpget

# snmpget -c public 10.32.5.18 ifHCInOctets.1

snmpget Agent reported error with variable #1.

.iso.org.dod.internet.mgmt.mib-2.ifMIB.ifMIBObjects.ifXTable.ifXEntry.

ifHCInOctets.1

SNMP Variable does not exist or access is denied.

Same query with SNMPv2C

# snmpget -v 2c -c public 10.32.5.18 ifHCInOctets.1

ifMIB.ifMIBObjects.ifXTable.ifXEntry.ifHCInOctets.1 Counter64 622366215

Q. Which Cisco devices implement 64-bit SNMP counters, especially for the IF-MIB?

A.These Cisco devices implement 64-bit SNMP counters:

Note: You must be a registered user and you must be logged in in order to visit the Cisco bug ID links and see detailed bug information.

- Cisco 2500, 2600 routers—These routers do not support 64-bit counters.

- Catalyst 2950 and 3550—Support begins in Cisco IOS Software Release 12.1(11)EA1 since Cisco bug ID CSCdx67611 and Cisco bug ID CSCdw52807 .

- Catalyst 2900XL and 3500XL—Support begins in Cisco IOS Software Release 12.0(5)WC3 since Cisco bug ID CSCds45300.

- Catalyst 5000 series—Since Cisco IOS Software Release 3.x. On RSM/RSFC, support begins in Cisco IOS Software Release 12.1(6)E1 since Cisco bug ID CSCds50549 .

- Catalyst 5000/6000 ATM modules—Since Cisco IOS Software Release 12.0(14)W05(20), refer to Cisco bug ID CSCds07238.

- Catalyst 6000 Gigabit Ethernet WAN OSM—Since Cisco IOS Software Release 12.1.12E, refer to Cisco bug ID CSCdw64849 .

- Catalyst 6000 series—All Cisco IOS software releases. WS-F6K-MSFC and MSM support begins in Cisco IOS Software Release 12.1(8a)E4.

- Catalyst 8500 series—Support begins as of Cisco IOS Software Release 12.0(5)W5(13).

- Tunnel interfaces—As of Cisco IOS Software Release 12.0(16)S, refer to Cisco bug ID CSCdt58029.

Note: Cisco IOS Software does not support 64-bit counters for interface speeds of less than 20 Mbps. This means that 64-bit counters are not supported on 10 Mb Ethernet ports. Only 100 Mb Fast-Ethernet and other high speed ports support 64-bit counters.

Q. Are ifInOctets and ifOutOctets SNMP counters the same as the show interfaces In/Out counters?

A.Yes, but only when SNMP is enabled from boot time. If you power on a Cisco device, then enable SNMP, the SNMP counters start from 0. They do not automatically pick up their values from the CLI output.

Q. Do the ifInOctets and ifOutOctets counters include framing overhead (Point-to-Point Protocol, High-Level Data Link Control)?

A.Yes.

Q. On an Asynchronous Transfer Mode interface, do the counters include the cell header?

A.Asynchronous Transfer Mode (ATM) counters do not include ATM overhead (cell headers and AAL5 padding).

Q. Why do SNMP counters not return the same number as CLIshowcommands?

A.An SNMP object defined as a Counter must abide by RFC1155 "3.2.3.3. Counter.

This application-wide type represents a non-negative integer which monotonically increases until it reaches a maximum value, when it wraps around and starts increasing again from zero. This memo specifies a maximum value of 2^32-1 (4294967295 decimal) for counters."

There are no methods to reset an SNMP counter to zero without the need to reload the device.

The counter output from a CLI show command can be reset on interfaces since the SNMP restrictions are not present.

The original interface counters defined in MIB-2 are 32-bit counters. For a 10 Mbps interface, a 32-bit counter could theoretically wrap in 57 minutes. It is easy to avoid discontinuities with such a long period. But for 100 Mbps, the minimum theoretical wrap time is 5.7 minutes. For 1 Gbps interfaces, it falls to 34 seconds. Granted these times are for transmission of back-to-back full-sized packets, a theoretical ideal. Even so, the higher the interface speed, the harder it becomes to avoid missing a counter wrap. As a solution to this problem, SNMPv2 SMI defined a new object type, counter64, for 64-bit counters. Therefore, there are several new 64-bit counters defined in the extension interface table (ifxTable) defined in RFC 1573(later superceded by RFC 2233). These are from the IF-MIB-V1SMI.my.

ifHCInOctets(.1.3.6.1.2.1.31.1.1.1.6)

ifHCOutOctets(1.3.6.1.2.1.31.1.1.1.10)

ifHCInUcastPkts(.1.3.6.1.2.1.31.1.1.1.7)

ifHCOutUcastPkts(.1.3.6.1.2.1.31.1.1.1.11)

ifHCInMulticastPkts(.1.3.6.1.2.1.31.1.1.1.8)

ifHCOutMulticastPkts(.1.3.6.1.2.1.31.1.1.1.12)

ifHCInBroadcastPkts(.1.3.6.1.2.1.31.1.1.1.9)

ifHCOutBroadcastPkts(.1.3.6.1.2.1.31.1.1.1.13)

Note: Only registered Cisco users can access internal Cisco information and tools

Although basic support for 64-bit counters was written into Cisco IOS Software Release 11.3, which starts from Cisco IOS Software Release 12.0, only ifHCInOctets (.1.3.6.1.2.1.31.1.1.1.6) and ifHCOutOctets (1.3.6.1.2.1.31.1.1.1.10) have been implemented for ATM LANE LEC sub-interfaces only. For Catalyst workgroup switches, 64-bit counter support has been implemented in version 3.1.

Note: You must use SNMPv2c or SNMPv3 protocol in order to retrieve any counter 64 objects.

SNMP Counters and show Command Equivalent Questions

Q. What do Cisco routers do for these SNMP MIB variables: ifInOctets, ifInUcastPkts, ifInNUcastPkts, ifInDiscards, ifInErrors, ifInUnknownProtos, ifOutOctets, ifOutUcastPkts, ifOutNUcastPkts, ifOutDiscards, ifOutErrors, and ifOutQLen?

Note: Only registered Cisco users can access internal Cisco information and tools

A.See this table for details. These are from the RFC1213-MIB.

ifInNUcastPkts (.1.3.6.1.2.1.2.2.1.12)

These are counts of inbound broadcast and multicast packets.

ifInDiscards (.1.3.6.1.2.1.2.2.1.13)

These are counted as no buffers as reflected in the show interfacescommand.

ifInErrors (.1.3.6.1.2.1.2.2.1.14)

These are counts of all input errors as reflected in the show interfacescommand.

ifInUnknownProtos (.1.3.6.1.2.1.2.2.1.15)

These are counted as unclassified errors.

ifOutOctets (.1.3.6.1.2.1.2.2.1.16)

These are counts of the number of bytes output by the interface as shown in the show interfacescommand.

ifOutUcastPkts (.1.3.6.1.2.1.2.2.1.17)

These are counts of outbound broadcast and multicast packets.

ifOutDiscards (.1.3.6.1.2.1.2.2.1.19)

These are counted as output drops as shown in the show interfacescommand.

ifOutErrors (.1.3.6.1.2.1.2.2.1.20)

These are counted as output errors as shown in the show interfacescommand.

ifOutQLen (.1.3.6.1.2.1.2.2.1.21)

This is the number of packets allowed to be on the output queue as shown in the show interfacescommand.

The variables previously listed that do not say they appear inshow interfacesare not available anywhere other than SNMP.

Examples

This example uses a 3640 that runs with Cisco IOS Software Release12.2(2)T1. The Read-Only (RO) Community String used is public and the Read-Write(RW) Community String used is private. Refer to How to Configure SNMP Community Strings for more information on how to configure SNMP Community Strings on devices.

This output is typical of theshow ip interface briefcommand executed in enable mode:

3600#show ip interface brief

Interface    IP-Address      OK? Method Status  Prol

BRI0/0       unassigned      YES NVRAM  administratively down dow

FastEthernet0/0     172.16.99.20    YES NVRAM  up      up

Serial0/0    unassigned      YES NVRAM  down    dow

Serial0/0.1  unassigned      YES unset  down    dow

BRI0/0:1     unassigned      YES unset  administratively down dow

BRI0/0:2     unassigned      YES unset  administratively down dow

Serial0/1    unassigned      YES NVRAM  administratively down dow

ATM1/0       unassigned      YES NVRAM  down    dow

ATM1/0.109   10.164.0.46     YES NVRAM  down    dow

Virtual-Template1   192.168.99.99     YES NVRAM  down    dow

Loopback0    10.1.10.1       YES NVRAM  up      up

Loopback1    unassigned      YES NVRAM  up      up

Loopback101  10.3.3.3  YES NVRAM  administratively down dow

Loopback200  10.4.4.14 YES NVRAM  administratively down dow

Loopback201  10.4.4.18 YES NVRAM  administratively down dow

This output is the MIB Object if Descr (.1.3.6.1.2.1.2.2.1.2)  for the previous router, which is a text string that contains information about the interface. This gives the interface name and description as obtained, which uses the previous CLI command output.  ifName (.1.3.6.1.2.1.31.1.1.1.1) can also be used but ifDescr gives the interface description along with the name, where ifName  only gives the interface name.

snmpwalk 172.16.99.20 public .1.3.6.1.2.1.2.2.1.2

interfaces.ifTable.ifEntry.ifDescr.1 = ATM1/0

interfaces.ifTable.ifEntry.ifDescr.2 = BRI0/0

interfaces.ifTable.ifEntry.ifDescr.3 = FastEthernet0/0

interfaces.ifTable.ifEntry.ifDescr.4 = Serial0/0

interfaces.ifTable.ifEntry.ifDescr.5 = BRI0/0:1

interfaces.ifTable.ifEntry.ifDescr.6 = BRI0/0:2

interfaces.ifTable.ifEntry.ifDescr.7 = Serial0/1

interfaces.ifTable.ifEntry.ifDescr.8 = Null0

interfaces.ifTable.ifEntry.ifDescr.10 = Foreign Exchange Office 2/0/0

interfaces.ifTable.ifEntry.ifDescr.11 = Foreign Exchange Office 2/0/1

interfaces.ifTable.ifEntry.ifDescr.12 = recEive And transMit 3/0/0

interfaces.ifTable.ifEntry.ifDescr.13 = recEive And transMit 3/0/1

interfaces.ifTable.ifEntry.ifDescr.14 = Loopback0

interfaces.ifTable.ifEntry.ifDescr.15 = Loopback1

interfaces.ifTable.ifEntry.ifDescr.16 = Loopback101

interfaces.ifTable.ifEntry.ifDescr.17 = Loopback200

interfaces.ifTable.ifEntry.ifDescr.18 = Loopback201

interfaces.ifTable.ifEntry.ifDescr.19 = Serial0/0.1

interfaces.ifTable.ifEntry.ifDescr.20 = ATM1/0.109-atm subif

interfaces.ifTable.ifEntry.ifDescr.21 = ATM1/0.109-aal5 layer

interfaces.ifTable.ifEntry.ifDescr.22 = Virtual-Template1

interfaces.ifTable.ifEntry.ifDescr.23 = Voice Encapsulation (POTS) Peer: 1

interfaces.ifTable.ifEntry.ifDescr.24 = Voice Over IP Peer: 2

interfaces.ifTable.ifEntry.ifDescr.25 = Voice Encapsulation (POTS) Peer: 111

interfaces.ifTable.ifEntry.ifDescr.26 = Voice Over IP Peer: 222

interfaces.ifTable.ifEntry.ifDescr.27 = Voice Over IP Peer: 1234

interfaces.ifTable.ifEntry.ifDescr.28 = Voice Over IP Peer: 300000

interfaces.ifTable.ifEntry.ifDescr.29 = Voice Over FR Peer: 3

interfaces.ifTable.ifEntry.ifDescr.30 = Voice Over IP Peer: 99

interfaces.ifTable.ifEntry.ifDescr.31 = Voice Encapsulation (POTS) Peer: 9

interfaces.ifTable.ifEntry.ifDescr.32 = BRI0/0-Physical

interfaces.ifTable.ifEntry.ifDescr.33 = BRI0/0-Signaling

interfaces.ifTable.ifEntry.ifDescr.34 = BRI0/0:1-Bearer Channel

interfaces.ifTable.ifEntry.ifDescr.35 = BRI0/0:2-Bearer Channel

1. ifInDiscards (.1.3.6.1.2.1.2.2.1.13):

snmpwalk 172.16.99.20 public .1.3.6.1.2.1.2.2.1.13

interfaces.ifTable.ifEntry.ifInDiscards.1 = Counter32: 0

interfaces.ifTable.ifEntry.ifInDiscards.2 = Counter32: 0

interfaces.ifTable.ifEntry.ifInDiscards.3 = Counter32: 0

interfaces.ifTable.ifEntry.ifInDiscards.4 = Counter32: 0

interfaces.ifTable.ifEntry.ifInDiscards.5 = Counter32: 0

interfaces.ifTable.ifEntry.ifInDiscards.6 = Counter32: 0

interfaces.ifTable.ifEntry.ifInDiscards.7 = Counter32: 0

interfaces.ifTable.ifEntry.ifInDiscards.8 = Counter32: 0

interfaces.ifTable.ifEntry.ifInDiscards.10 = Counter32: 0

interfaces.ifTable.ifEntry.ifInDiscards.11 = Counter32: 0

interfaces.ifTable.ifEntry.ifInDiscards.12 = Counter32: 0

interfaces.ifTable.ifEntry.ifInDiscards.13 = Counter32: 0

interfaces.ifTable.ifEntry.ifInDiscards.14 = Counter32: 0

interfaces.ifTable.ifEntry.ifInDiscards.15 = Counter32: 0

interfaces.ifTable.ifEntry.ifInDiscards.16 = Counter32: 0

interfaces.ifTable.ifEntry.ifInDiscards.17 = Counter32: 0

interfaces.ifTable.ifEntry.ifInDiscards.18 = Counter32: 0

interfaces.ifTable.ifEntry.ifInDiscards.19 = Counter32: 0

interfaces.ifTable.ifEntry.ifInDiscards.20 = Counter32: 0

interfaces.ifTable.ifEntry.ifInDiscards.21 = Counter32: 0

interfaces.ifTable.ifEntry.ifInDiscards.22 = Counter32: 0

interfaces.ifTable.ifEntry.ifInDiscards.23 = Counter32: 0

interfaces.ifTable.ifEntry.ifInDiscards.24 = Counter32: 0

interfaces.ifTable.ifEntry.ifInDiscards.25 = Counter32: 0

interfaces.ifTable.ifEntry.ifInDiscards.26 = Counter32: 0

interfaces.ifTable.ifEntry.ifInDiscards.27 = Counter32: 0

interfaces.ifTable.ifEntry.ifInDiscards.28 = Counter32: 0

interfaces.ifTable.ifEntry.ifInDiscards.29 = Counter32: 0

interfaces.ifTable.ifEntry.ifInDiscards.30 = Counter32: 0

interfaces.ifTable.ifEntry.ifInDiscards.31 = Counter32: 0

interfaces.ifTable.ifEntry.ifInDiscards.32 = Counter32: 0

interfaces.ifTable.ifEntry.ifInDiscards.33 = Counter32: 0

interfaces.ifTable.ifEntry.ifInDiscards.34 = Counter32: 0

interfaces.ifTable.ifEntry.ifInDiscards.35 = Counter32: 0

The ifInDiscardsis zero for all the interfaces of this router. If you compare this with the CLI result of the show interfaces fastEthernet 0/0 command, this confirms the result:

3600#show interfaces fastEthernet 0/0

FastEthernet0/0 is up, line protocol is up

Hardware is AmdFE, address is 0001.42b4.fe81 (bia 0001.42b4.fe81)

Description: testme

Internet address is 172.16.99.20/24

MTU 1500 bytes, BW 100000 Kbit, DLY 100 usec,

reliability 255/255, txload 1/255, rxload 1/255

Encapsulation ARPA, loopback not set

Keepalive set (10 sec)

Full-duplex, 100Mb/s, 100BaseTX/FX

ARP type: ARPA, ARP Timeout 04:00:00

Last input 00:00:00, output 00:00:00, output hang never

Last clearing of "show interface" counters never

Queueing strategy: fifo

Output queue 0/40, 0 drops; input queue 0/75, 323 drops

5 minute input rate 1000 bits/sec, 2 packets/sec

5 minute output rate 0 bits/sec, 0 packets/sec

1767411 packets input, 178272010 bytes

Received 1161500 broadcasts, 0 runts, 0 giants, 0 throttles

0 input errors, 0 CRC, 0 frame, 0 overrun, 0 ignored

0 watchdog

0 input packets with dribble condition detected

7146925 packets output, 765049281 bytes, 0 underruns(0/0/0)

0 output errors, 0 collisions, 1 interface resets

0 babbles, 0 late collision, 461 deferred

0 lost carrier, 0 no carrier

0 output buffer failures, 0 output buffers swapped out

2. ifInErrors (.1.3.6.1.2.1.2.2.1.14):

snmpwalk 172.16.99.20 public .1.3.6.1.2.1.2.2.1.14

interfaces.ifTable.ifEntry.ifInErrors.1 = Counter32: 0

interfaces.ifTable.ifEntry.ifInErrors.2 = Counter32: 0

interfaces.ifTable.ifEntry.ifInErrors.3 = Counter32: 0

interfaces.ifTable.ifEntry.ifInErrors.4 = Counter32: 0

interfaces.ifTable.ifEntry.ifInErrors.5 = Counter32: 0

interfaces.ifTable.ifEntry.ifInErrors.6 = Counter32: 0

interfaces.ifTable.ifEntry.ifInErrors.7 = Counter32: 1

interfaces.ifTable.ifEntry.ifInErrors.8 = Counter32: 0

interfaces.ifTable.ifEntry.ifInErrors.10 = Counter32: 0

interfaces.ifTable.ifEntry.ifInErrors.11 = Counter32: 0

interfaces.ifTable.ifEntry.ifInErrors.12 = Counter32: 0

interfaces.ifTable.ifEntry.ifInErrors.13 = Counter32: 0

interfaces.ifTable.ifEntry.ifInErrors.14 = Counter32: 0

interfaces.ifTable.ifEntry.ifInErrors.15 = Counter32: 0

interfaces.ifTable.ifEntry.ifInErrors.16 = Counter32: 0

interfaces.ifTable.ifEntry.ifInErrors.17 = Counter32: 0

interfaces.ifTable.ifEntry.ifInErrors.18 = Counter32: 0

interfaces.ifTable.ifEntry.ifInErrors.19 = Counter32: 0

interfaces.ifTable.ifEntry.ifInErrors.20 = Counter32: 0

interfaces.ifTable.ifEntry.ifInErrors.21 = Counter32: 0

interfaces.ifTable.ifEntry.ifInErrors.22 = Counter32: 0

interfaces.ifTable.ifEntry.ifInErrors.23 = Counter32: 0

interfaces.ifTable.ifEntry.ifInErrors.24 = Counter32: 0

interfaces.ifTable.ifEntry.ifInErrors.25 = Counter32: 0

interfaces.ifTable.ifEntry.ifInErrors.26 = Counter32: 0

interfaces.ifTable.ifEntry.ifInErrors.27 = Counter32: 0

interfaces.ifTable.ifEntry.ifInErrors.28 = Counter32: 0

interfaces.ifTable.ifEntry.ifInErrors.29 = Counter32: 0

interfaces.ifTable.ifEntry.ifInErrors.30 = Counter32: 0

interfaces.ifTable.ifEntry.ifInErrors.31 = Counter32: 0

interfaces.ifTable.ifEntry.ifInErrors.32 = Counter32: 0

interfaces.ifTable.ifEntry.ifInErrors.33 = Counter32: 0

interfaces.ifTable.ifEntry.ifInErrors.34 = Counter32: 0

interfaces.ifTable.ifEntry.ifInErrors.35 = Counter32: 0

This output shows that there is only one input error for the interface  interfaces.ifTable.ifEntry.ifInErrors.7 = Counter32: 1.

In order to determine which interface this is, compare it with the output of ifDescrabove, which shows that this is from interfaces.ifTable.ifEntry.ifDescr.7 = Serial0/1.  Now execute the show interfaces serial 0/1 command in enable mode in order to verify the previous result:

3600#show interfaces serial 0/1

Serial0/1 is administratively down, line protocol is down

Hardware is DSCC4 Serial

Description: atm-dxi test

MTU 1500 bytes, BW 2048 Kbit, DLY 20000 usec,

reliability 255/255, txload 1/255, rxload 1/255

Encapsulation ATM-DXI, loopback not set

Keepalive not set

Last input never, output never, output hang never

Last clearing of "show interface" counters 1w1d

Queueing strategy: fifo

Output queue 0/40, 0 drops; input queue 0/75, 0 drops

5 minute input rate 0 bits/sec, 0 packets/sec

5 minute output rate 0 bits/sec, 0 packets/sec

0 packets input, 0 bytes, 0 no buffer

Received 0 broadcasts, 0 runts, 0 giants, 0 throttles

1 input errors, 0 CRC, 0 frame, 0 overrun, 0 ignored, 1 abort

0 packets output, 0 bytes, 0 underruns

0 output errors, 0 collisions, 0 interface resets

0 output buffer failures, 0 output buffers swapped out

0 carrier transitions

DCD=down  DSR=down  DTR=down  RTS=down  CTS=down

3. ifOutOctets (.1.3.6.1.2.1.2.2.1.16):

snmpwalk 172.16.99.20 public .1.3.6.1.2.1.2.2.1.16

interfaces.ifTable.ifEntry.ifOutOctets.1 = Counter32: 98

interfaces.ifTable.ifEntry.ifOutOctets.2 = Counter32: 0

interfaces.ifTable.ifEntry.ifOutOctets.3 = Counter32: 765470674

interfaces.ifTable.ifEntry.ifOutOctets.4 = Counter32: 0

interfaces.ifTable.ifEntry.ifOutOctets.5 = Counter32: 0

interfaces.ifTable.ifEntry.ifOutOctets.6 = Counter32: 0

interfaces.ifTable.ifEntry.ifOutOctets.7 = Counter32: 0

interfaces.ifTable.ifEntry.ifOutOctets.8 = Counter32: 0

interfaces.ifTable.ifEntry.ifOutOctets.10 = Counter32: 0

interfaces.ifTable.ifEntry.ifOutOctets.11 = Counter32: 0

interfaces.ifTable.ifEntry.ifOutOctets.12 = Counter32: 0

interfaces.ifTable.ifEntry.ifOutOctets.13 = Counter32: 0

interfaces.ifTable.ifEntry.ifOutOctets.14 = Counter32: 0

interfaces.ifTable.ifEntry.ifOutOctets.15 = Counter32: 0

interfaces.ifTable.ifEntry.ifOutOctets.16 = Counter32: 0

interfaces.ifTable.ifEntry.ifOutOctets.17 = Counter32: 0

interfaces.ifTable.ifEntry.ifOutOctets.18 = Counter32: 0

interfaces.ifTable.ifEntry.ifOutOctets.19 = Counter32: 0

interfaces.ifTable.ifEntry.ifOutOctets.20 = Counter32: 0

interfaces.ifTable.ifEntry.ifOutOctets.21 = Counter32: 98

interfaces.ifTable.ifEntry.ifOutOctets.22 = Counter32: 0

interfaces.ifTable.ifEntry.ifOutOctets.23 = Counter32: 0

interfaces.ifTable.ifEntry.ifOutOctets.24 = Counter32: 0

interfaces.ifTable.ifEntry.ifOutOctets.25 = Counter32: 0

interfaces.ifTable.ifEntry.ifOutOctets.26 = Counter32: 0

interfaces.ifTable.ifEntry.ifOutOctets.27 = Counter32: 0

interfaces.ifTable.ifEntry.ifOutOctets.28 = Counter32: 0

interfaces.ifTable.ifEntry.ifOutOctets.29 = Counter32: 0

interfaces.ifTable.ifEntry.ifOutOctets.30 = Counter32: 0

interfaces.ifTable.ifEntry.ifOutOctets.31 = Counter32: 0

interfaces.ifTable.ifEntry.ifOutOctets.32 = Counter32: 0

interfaces.ifTable.ifEntry.ifOutOctets.33 = Counter32: 0

interfaces.ifTable.ifEntry.ifOutOctets.34 = Counter32: 0

interfaces.ifTable.ifEntry.ifOutOctets.35 = Counter32: 0

If you compare the previous result with the output of the ifDescr, this indicates:

- interfaces.ifTable.ifEntry.ifOutOctets.1 = Counter32: 98 corresponds with interfaces.ifTable.ifEntry.ifDescr.1 = ATM1/0

- interfaces.ifTable.ifEntry.ifOutOctets.3 = Counter32: 765470674 corresponds with interfaces.ifTable.ifEntry.ifDescr.3 = FastEthernet0/0

- interfaces.ifTable.ifEntry.ifOutOctets.21 = Counter32: 98 corresponds with interfaces.ifTable.ifEntry.ifDescr.21 = ATM1/0.109-aal5 layer

This is the output of the CLI show interfaces command for each of the previous interfaces executed in enable mode:

3600#show interfaces atM 1/0

ATM1/0 is down, line protocol is down

Hardware is RS8234 ATMOC3

MTU 4470 bytes, sub MTU 4470, BW 155000 Kbit, DLY 80 usec,

reliability 5/255, txload 1/255, rxload 1/255

Encapsulation ATM, loopback not set

Encapsulation(s): AAL5

1024 maximum active VCs, 1 current VCCs

VC idle disconnect time: 300 seconds

Last input never, output 1w1d, output hang never

Last clearing of "show interface" counters never

Input queue: 0/75/0/0 (size/max/drops/flushes); Total output drops: 0

Queueing strategy: None

5 minute input rate 0 bits/sec, 0 packets/sec

5 minute output rate 0 bits/sec, 0 packets/sec

0 packets input, 0 bytes, 0 no buffer

Received 0 broadcasts, 0 runts, 0 giants, 0 throttles

0 input errors, 0 CRC, 0 frame, 0 overrun, 0 ignored, 0 abort

2 packets output, 98 bytes, 0 underruns

0 output errors, 0 collisions, 2 interface resets

0 output buffer failures, 0 output buffers swapped out

3600#show interfaces fastEthernet 0/0

FastEthernet0/0 is up, line protocol is up

Hardware is AmdFE, address is 0001.42b4.fe81 (bia 0001.42b4.fe81)

Description: testme

Internet address is 172.16.99.20/24

MTU 1500 bytes, BW 100000 Kbit, DLY 100 usec,

reliability 255/255, txload 1/255, rxload 1/255

Encapsulation ARPA, loopback not set

Keepalive set (10 sec)

Full-duplex, 100Mb/s, 100BaseTX/FX

ARP type: ARPA, ARP Timeout 04:00:00

Last input 00:00:00, output 00:00:00, output hang never

Last clearing of "show interface" counters never

Queueing strategy: fifo

Output queue 0/40, 0 drops; input queue 0/75, 323 drops

5 minute input rate 2000 bits/sec, 3 packets/sec

5 minute output rate 1000 bits/sec, 1 packets/sec

1772214 packets input, 178767841 bytes

Received 1164210 broadcasts, 0 runts, 0 giants, 0 throttles

0 input errors, 0 CRC, 0 frame, 0 overrun, 0 ignored

0 watchdog

0 input packets with dribble condition detected

7149179 packets output, 765450524 bytes, 0 underruns(0/0/0)

0 output errors, 0 collisions, 1 interface resets

0 babbles, 0 late collision, 461 deferred

0 lost carrier, 0 no carrier

0 output buffer failures, 0 output buffers swapped out

The output of the ifOutOctetsdoes not match the CLI output for the show interfaces FastEthernet 0/0  command, but it is similar. This is because there can be a delay when the interfaces are polled and when the CLI command is executed.

3600#show interfaces atM 1/0.109

ATM1/0.109 is down, line protocol is down

Hardware is RS8234 ATMOC3

Description: pvc

Internet address is 10.164.0.46/30

MTU 4470 bytes, BW 2250 Kbit, DLY 80 usec,

reliability 5/255, txload 1/255, rxload 1/255

Encapsulation ATM

0 packets input, 0 bytes

2 packets output,98 bytes

0 OAM cells input, 77093 OAM cells output

AAL5 CRC errors : 0

AAL5 SAR Timeouts : 0

AAL5 Oversized SDUs : 0

AAL5 length violation : 0

AAL5 CPI Error : 0

4. ifOutDiscards (.1.3.6.1.2.1.2.2.1.19):

snmpwalk 172.16.99.20 public .1.3.6.1.2.1.2.2.1.19

interfaces.ifTable.ifEntry.ifOutDiscards.1 = Counter32: 0

interfaces.ifTable.ifEntry.ifOutDiscards.2 = Counter32: 0

interfaces.ifTable.ifEntry.ifOutDiscards.3 = Counter32: 0

interfaces.ifTable.ifEntry.ifOutDiscards.4 = Counter32: 0

interfaces.ifTable.ifEntry.ifOutDiscards.5 = Counter32: 0

interfaces.ifTable.ifEntry.ifOutDiscards.6 = Counter32: 0

interfaces.ifTable.ifEntry.ifOutDiscards.7 = Counter32: 0

interfaces.ifTable.ifEntry.ifOutDiscards.8 = Counter32: 0

interfaces.ifTable.ifEntry.ifOutDiscards.10 = Counter32: 0

interfaces.ifTable.ifEntry.ifOutDiscards.11 = Counter32: 0

interfaces.ifTable.ifEntry.ifOutDiscards.12 = Counter32: 0

interfaces.ifTable.ifEntry.ifOutDiscards.13 = Counter32: 0

interfaces.ifTable.ifEntry.ifOutDiscards.14 = Counter32: 0

interfaces.ifTable.ifEntry.ifOutDiscards.15 = Counter32: 0

interfaces.ifTable.ifEntry.ifOutDiscards.16 = Counter32: 0

interfaces.ifTable.ifEntry.ifOutDiscards.17 = Counter32: 0

interfaces.ifTable.ifEntry.ifOutDiscards.18 = Counter32: 0

interfaces.ifTable.ifEntry.ifOutDiscards.19 = Counter32: 0

interfaces.ifTable.ifEntry.ifOutDiscards.20 = Counter32: 0

interfaces.ifTable.ifEntry.ifOutDiscards.21 = Counter32: 0

interfaces.ifTable.ifEntry.ifOutDiscards.22 = Counter32: 0

interfaces.ifTable.ifEntry.ifOutDiscards.23 = Counter32: 0

interfaces.ifTable.ifEntry.ifOutDiscards.24 = Counter32: 0

interfaces.ifTable.ifEntry.ifOutDiscards.25 = Counter32: 0

interfaces.ifTable.ifEntry.ifOutDiscards.26 = Counter32: 0

interfaces.ifTable.ifEntry.ifOutDiscards.27 = Counter32: 0

interfaces.ifTable.ifEntry.ifOutDiscards.28 = Counter32: 0

interfaces.ifTable.ifEntry.ifOutDiscards.29 = Counter32: 0

interfaces.ifTable.ifEntry.ifOutDiscards.30 = Counter32: 0

interfaces.ifTable.ifEntry.ifOutDiscards.31 = Counter32: 0

interfaces.ifTable.ifEntry.ifOutDiscards.32 = Counter32: 0

interfaces.ifTable.ifEntry.ifOutDiscards.33 = Counter32: 0

interfaces.ifTable.ifEntry.ifOutDiscards.34 = Counter32: 0

interfaces.ifTable.ifEntry.ifOutDiscards.35 = Counter32: 0

The ifOutDiscards is zero for all the interfaces. With the show interfaces fastEthernet 0/0  command as an example, this command produces this result:

3600#show interfaces fastEthernet 0/0

FastEthernet0/0 is up, line protocol is up

Hardware is AmdFE, address is 0001.42b4.fe81 (bia 0001.42b4.fe81)

Description: testme

Internet address is 172.16.99.20/24

MTU 1500 bytes, BW 100000 Kbit, DLY 100 usec,

reliability 255/255, txload 1/255, rxload 1/255

Encapsulation ARPA, loopback not set

Keepalive set (10 sec)

Full-duplex, 100Mb/s, 100BaseTX/FX

ARP type: ARPA, ARP Timeout 04:00:00

Last input 00:00:00, output 00:00:00, output hang never

Last clearing of "show interface" counters never

Queueing strategy: fifo

Output queue 0/40, 0 drops; input queue 0/75, 323 drops

5 minute input rate 1000 bits/sec, 2 packets/sec

5 minute output rate 1000 bits/sec, 1 packets/sec

1774581 packets input, 179005552 bytes

Received 1165620 broadcasts, 0 runts, 0 giants, 0 throttles

0 input errors, 0 CRC, 0 frame, 0 overrun, 0 ignored

0 watchdog

0 input packets with dribble condition detected

7150259 packets output, 765645035 bytes, 0 underruns(0/0/0)

0 output errors, 0 collisions, 1 interface resets

0 babbles, 0 late collision, 461 deferred

0 lost carrier, 0 no carrier

0 output buffer failures, 0 output buffers swapped out

5. ifOutErrors (.1.3.6.1.2.1.2.2.1.20):

snmpwalk 172.16.99.20 public .1.3.6.1.2.1.2.2.1.20

interfaces.ifTable.ifEntry.ifOutErrors.1 = Counter32: 0

interfaces.ifTable.ifEntry.ifOutErrors.2 = Counter32: 0

interfaces.ifTable.ifEntry.ifOutErrors.3 = Counter32: 0

interfaces.ifTable.ifEntry.ifOutErrors.4 = Counter32: 0

interfaces.ifTable.ifEntry.ifOutErrors.5 = Counter32: 0

interfaces.ifTable.ifEntry.ifOutErrors.6 = Counter32: 0

interfaces.ifTable.ifEntry.ifOutErrors.7 = Counter32: 0

interfaces.ifTable.ifEntry.ifOutErrors.8 = Counter32: 0

interfaces.ifTable.ifEntry.ifOutErrors.10 = Counter32: 0

interfaces.ifTable.ifEntry.ifOutErrors.11 = Counter32: 0

interfaces.ifTable.ifEntry.ifOutErrors.12 = Counter32: 0

interfaces.ifTable.ifEntry.ifOutErrors.13 = Counter32: 0

interfaces.ifTable.ifEntry.ifOutErrors.14 = Counter32: 0

interfaces.ifTable.ifEntry.ifOutErrors.15 = Counter32: 0

interfaces.ifTable.ifEntry.ifOutErrors.16 = Counter32: 0

interfaces.ifTable.ifEntry.ifOutErrors.17 = Counter32: 0

interfaces.ifTable.ifEntry.ifOutErrors.18 = Counter32: 0

interfaces.ifTable.ifEntry.ifOutErrors.19 = Counter32: 0

interfaces.ifTable.ifEntry.ifOutErrors.20 = Counter32: 0

interfaces.ifTable.ifEntry.ifOutErrors.21 = Counter32: 0

interfaces.ifTable.ifEntry.ifOutErrors.22 = Counter32: 0

interfaces.ifTable.ifEntry.ifOutErrors.23 = Counter32: 0

interfaces.ifTable.ifEntry.ifOutErrors.24 = Counter32: 0

interfaces.ifTable.ifEntry.ifOutErrors.25 = Counter32: 0

interfaces.ifTable.ifEntry.ifOutErrors.26 = Counter32: 0

interfaces.ifTable.ifEntry.ifOutErrors.27 = Counter32: 0

interfaces.ifTable.ifEntry.ifOutErrors.28 = Counter32: 0

interfaces.ifTable.ifEntry.ifOutErrors.29 = Counter32: 0

interfaces.ifTable.ifEntry.ifOutErrors.30 = Counter32: 0

interfaces.ifTable.ifEntry.ifOutErrors.31 = Counter32: 0

interfaces.ifTable.ifEntry.ifOutErrors.32 = Counter32: 0

interfaces.ifTable.ifEntry.ifOutErrors.33 = Counter32: 0

interfaces.ifTable.ifEntry.ifOutErrors.34 = Counter32: 0

interfaces.ifTable.ifEntry.ifOutErrors.35 = Counter32: 0

The ifOutErrorsis zero for all the interfaces. With the show interfaces fastEthernet 0/0  command as an example, this command produces this result:

3600#show interfaces fastEthernet 0/0

FastEthernet0/0 is up, line protocol is up

Hardware is AmdFE, address is 0001.42b4.fe81 (bia 0001.42b4.fe81)

Description: testme

Internet address is 172.16.99.20/24

MTU 1500 bytes, BW 100000 Kbit, DLY 100 usec,

reliability 255/255, txload 1/255, rxload 1/255

Encapsulation ARPA, loopback not set

Keepalive set (10 sec)

Full-duplex, 100Mb/s, 100BaseTX/FX

ARP type: ARPA, ARP Timeout 04:00:00

Last input 00:00:00, output 00:00:00, output hang never

Last clearing of "show interface" counters never

Queueing strategy: fifo

Output queue 0/40, 0 drops; input queue 0/75, 323 drops

5 minute input rate 0 bits/sec, 1 packets/sec

5 minute output rate 0 bits/sec, 0 packets/sec

1776187 packets input, 179154616 bytes

Received 1166778 broadcasts, 0 runts, 0 giants, 0 throttles

0 input errors, 0 CRC, 0 frame, 0 overrun, 0 ignored

0 watchdog

0 input packets with dribble condition detected

7150781 packets output, 765744231 bytes, 0 underruns(0/0/0)

0 output errors, 0 collisions, 1 interface resets

0 babbles, 0 late collision, 461 deferred

0 lost carrier, 0 no carrier

0 output buffer failures, 0 output buffers swapped out

6. ifOutQLen (.1.3.6.1.2.1.2.2.1.21):

snmpwalk 172.16.99.20 public .1.3.6.1.2.1.2.2.1.21

interfaces.ifTable.ifEntry.ifOutQLen.1 = Gauge32: 0

interfaces.ifTable.ifEntry.ifOutQLen.2 = Gauge32: 0

interfaces.ifTable.ifEntry.ifOutQLen.3 = Gauge32: 0

interfaces.ifTable.ifEntry.ifOutQLen.4 = Gauge32: 0

interfaces.ifTable.ifEntry.ifOutQLen.5 = Gauge32: 0

interfaces.ifTable.ifEntry.ifOutQLen.6 = Gauge32: 0

interfaces.ifTable.ifEntry.ifOutQLen.7 = Gauge32: 0

interfaces.ifTable.ifEntry.ifOutQLen.8 = Gauge32: 0

interfaces.ifTable.ifEntry.ifOutQLen.10 = Gauge32: 0

interfaces.ifTable.ifEntry.ifOutQLen.11 = Gauge32: 0

interfaces.ifTable.ifEntry.ifOutQLen.12 = Gauge32: 0

interfaces.ifTable.ifEntry.ifOutQLen.13 = Gauge32: 0

interfaces.ifTable.ifEntry.ifOutQLen.14 = Gauge32: 0

interfaces.ifTable.ifEntry.ifOutQLen.15 = Gauge32: 0

interfaces.ifTable.ifEntry.ifOutQLen.16 = Gauge32: 0

interfaces.ifTable.ifEntry.ifOutQLen.17 = Gauge32: 0

interfaces.ifTable.ifEntry.ifOutQLen.18 = Gauge32: 0

interfaces.ifTable.ifEntry.ifOutQLen.19 = Gauge32: 0

interfaces.ifTable.ifEntry.ifOutQLen.20 = Gauge32: 0

interfaces.ifTable.ifEntry.ifOutQLen.21 = Gauge32: 0

interfaces.ifTable.ifEntry.ifOutQLen.22 = Gauge32: 0

interfaces.ifTable.ifEntry.ifOutQLen.23 = Gauge32: 0

interfaces.ifTable.ifEntry.ifOutQLen.24 = Gauge32: 0

interfaces.ifTable.ifEntry.ifOutQLen.25 = Gauge32: 0

interfaces.ifTable.ifEntry.ifOutQLen.26 = Gauge32: 0

interfaces.ifTable.ifEntry.ifOutQLen.27 = Gauge32: 0

interfaces.ifTable.ifEntry.ifOutQLen.28 = Gauge32: 0

interfaces.ifTable.ifEntry.ifOutQLen.29 = Gauge32: 0

interfaces.ifTable.ifEntry.ifOutQLen.30 = Gauge32: 0

interfaces.ifTable.ifEntry.ifOutQLen.31 = Gauge32: 0

interfaces.ifTable.ifEntry.ifOutQLen.32 = Gauge32: 0

interfaces.ifTable.ifEntry.ifOutQLen.33 = Gauge32: 0

interfaces.ifTable.ifEntry.ifOutQLen.34 = Gauge32: 0

interfaces.ifTable.ifEntry.ifOutQLen.35 = Gauge32: 0

The ifOutQLenis zero for all the interfaces. With the show interfaces fastEthernet 0/0 command as an example:

3600#show interfaces fastEthernet 0/0

FastEthernet0/0 is up, line protocol is up

Hardware is AmdFE, address is 0001.42b4.fe81 (bia 0001.42b4.fe81)

Description: testme

Internet address is 172.16.99.20/24

MTU 1500 bytes, BW 100000 Kbit, DLY 100 usec,

reliability 255/255, txload 1/255, rxload 1/255

Encapsulation ARPA, loopback not set

Keepalive set (10 sec)

Full-duplex, 100Mb/s, 100BaseTX/FX

ARP type: ARPA, ARP Timeout 04:00:00

Last input 00:00:00, output 00:00:00, output hang never

Last clearing of "show interface" counters never

Queueing strategy: fifo

Output queue 0/40, 0 drops; input queue 0/75, 323 drops

5 minute input rate 0 bits/sec, 1 packets/sec

5 minute output rate 0 bits/sec, 0 packets/sec

1776912 packets input, 179225431 bytes

Received 1167240 broadcasts, 0 runts, 0 giants, 0 throttles

0 input errors, 0 CRC, 0 frame, 0 overrun, 0 ignored

0 watchdog

0 input packets with dribble condition detected

7151102 packets output, 765796341 bytes, 0 underruns(0/0/0)

0 output errors, 0 collisions, 1 interface resets

0 babbles, 0 late collision, 461 deferred

0 lost carrier, 0 no carrier

0 output buffer failures, 0 output buffers swapped out

Q. What is the relationship between theshow interfacesstatementsno buffersandinput queue drops? Why do the inDiscards of SNMP giveno bufferscounts and notinput queue drops, while the outDiscards of SNMP do giveoutput queue drops?

A.The locIfInputQueueDrops/ifInDiscards work differently than locIfOutputQueueDrops/ifOutDiscards. The ifInDiscards counts the number of packets that are thrown away for lack of a system resource such as a buffer. This is generally a subset of the locIfInputQueueDrops. You often see locIfInputQueueDrops = ifInDiscards. But, locIfInputQueueDrops also counts the number of packets dropped because they hit the input queue limit. So generally, you see locIfInputQueueDrops > ifInDiscards.

Summary

locIfInputQueueDrops = Queue Limit Drops + No Buffer Drops ifInDiscards = No Buffer Drops (and is a subset of locIfInputQueueDrops)

The locIfOutputQueueDrops and ifOutDiscards are always equal when they count the same events. Those events hit the output queue limit, and do not have a hardware tx buffer when a packet is fastswitched from one interface to another. The OIDs of the previous MIB Objects are these:

FromOLD-CISCO-INTERFACES-MIB

FromRFC1213-MIB

locIfInputQueueDrops = .1.3.6.1.4.1.9.2.2.1.1.26

ifInDiscards = .1.3.6.1.2.1.2.2.1.13

locIfOutputQueueDrops = .1.3.6.1.4.1.9.2.2.1.1.27

ifOutDiscards = .1.3.6.1.2.1.2.2.1.19

Q. Can I poll no buffers on a router?

A.Yes. You can poll for ifInDiscards in order to poll no buffers.

Q. How do I poll queue limit drops on a router?

A.With the use of SNMP, there is no way for the show interfaces command to break out the individual elements that go into the output drops.

Consider this new information about what goes into the output drops counter:

Input drops = Queue limit drops + Throttling drops + SMT queue full drops + RSRB drops + no buffer drops

In addition, SNMP counters are never cleared, even if the interfaces are cleared.

Related Information

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