Performance Management Commands

See the Internetwork Design Guide for additional information.

For performance management configuration tasks and examples, refer to the chapter entitled "Managing System Performance" in the Configuration Fundamentals Configuration Guide.

Syntax Description

Default

Command Mode

Global configuration

Usage Guidelines

This command first appeared in Cisco IOS Release 10.0.

Normally you need not adjust these parameters; do so only after consulting with technical support personnel. Improper settings can adversely impact system performance.

You cannot configure FDDI buffers.

In the following example, the system will try to keep at least 50 small buffers free:

buffers small min-free 50
 

In the following example, the permanent buffer pool allocation for big buffers is increased to 200:

buffers big permanent 200

A general guideline is to display buffers with the show buffers command, observe which buffer pool is depleted, and increase that one.

In the following example, the permanent Ethernet 0 interface buffer pool on a Cisco 4000 is increased to 96 because the Ethernet 0 buffer pool is depleted:

buffers ethernet 0 permanent 96

Related Commands

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Syntax Description

Default

18024 bytes

Command Mode

Global configuration

Usage Guidelines

This command first appeared in Cisco IOS Release 10.0.

Use only after consulting with technical support personnel. The buffer size cannot be lowered below the default.

Example

In the following example, the system will resize huge buffers to 20000 bytes:

buffers huge size 20000

Related Commands

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Syntax Description

Default

No custom queue list is assigned.

Command Mode

Interface configuration

Usage Guidelines

This command first appeared in Cisco IOS Release 10.0.

Only one queue list can be assigned per interface. Use this command in place of the priority-list command (not in addition to it). Custom queueing allows a fairness not provided with priority queueing. With custom queueing, you can control the interfaces' available bandwidth when it is unable to accommodate the aggregate traffic enqueued. Associated with each output queue is a configurable byte count, which specifies how many bytes of data should be delivered from the current queue by the system before the system moves on to the next queue. When a particular queue is being processed, packets are sent until the number of bytes sent exceeds the queue byte count or until the queue is empty.

Use the show queueing custom and show interface commands to display the current status of the custom output queues.

Example

In the following example, custom queue list number 3 is assigned to serial interface 0:

interface serial 0
custom-queue-list 3

Related Commands

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Syntax Description

Default

Fair queueing is now enabled automatically on interfaces configured for Multilink PPP.

Congestive-discard-threshold: 64 messages; dynamic-queues: 256; reservable-queues: 0.

Command Mode

Interface configuration

Usage Guidelines

This command first appeared in Cisco IOS Release 11.0.

Fair queuing is supported for all LAN and line (WAN) protocols except X.25. These protocols are listed in "Default." Fair queuing is on by default for interfaces with bandwidth less than or equal to 2 Mbps.

Weighted fair queuing can manage duplex data streams, such as those between pairs of applications, and simplex data streams such as voice or video. From the perspective of weighted fair queueing, there are two categories of sessions: high-bandwidth sessions and low-bandwidth sessions. Low-bandwidth traffic has effective priority over high-bandwidth traffic, and high-bandwidth traffic shares the transmission service proportionally according to assigned weights.

When weighted fair queuing is enabled for an interface, new messages for high-bandwidth traffic streams are discarded after the configured or default congestive-messages threshold has been met. However, low-bandwidth conversations, which include control-message conversations, continue to enqueue data. As a result, the fair queue may occasionally contain more messages than its configured threshold number specifies.

It is important to note that IP precedence, congestion in Frame Relay switching, and discard eligibility flags affect the weights used for queuing.

Examples

The following example enables use of weighted fair queuing on Serial 0, with a congestive threshold of 300. This means that messages will be discarded from the queuing system only when 300 or more messages have been queued and the message is in a data stream that has more than one message in the queue. The transmit queue limit is set to 2, based on the 384-kilobit (kb) line set by the bandwidth command:

interface serial 0
 bandwidth 384
 fair-queue 300
 

The following example requests a fair queue with 512 dynamic queues, 18 RSVP queues, and a congestive discard threshold of 64 messages:

interface Serial 3/0
 ip unnumbered Ethernet 0/0
 fair-queue 64 512 18

Related Commands

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Syntax Description

Default

300 seconds (or 5 minutes)

Command Mode

Interface configuration

Usage Guidelines

This command first appeared in Cisco IOS Release 10.3.

If you want load computations to be more reactive to short bursts of traffic, rather than averaged over 5-minute periods, you can shorten the length of time over which load averages are computed.

If the load interval is set to 30 seconds, new data is used for load calculations over a 30-second period. This data is used to compute load statistics, including input rate in bits and packets per second, output rate in bits and packets per second, load, and reliability.

Load data is gathered every 5 seconds. This data is used for a weighted average calculation in which more-recent load data has more weight in the computation than older load data. If the load interval is set to 30 seconds, the average is computed for the last 30 seconds of load data.

The load-interval command allows you to change the default interval of 5 minutes to a shorter or longer period of time. If you change it to a shorter period of time, the input and output statistics that are displayed when you use the show interface command will be more current, and based on more instantaneous data, rather than reflecting a more average load over a longer period of time.

This command is often used for dial backup purposes, to increase or decrease the likelihood of a backup interface being implemented, but it can be used on any interface.

Example

In the following example, the default 5-minute average is set it to a 30-second average. A burst in traffic that would not trigger a dial backup for an interface configured with the default 5-minute interval might trigger a dial backup for this interface that is set for a shorter, 30-second interval.

interface serial 0
 load-interval 30

Related Commands

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show interfaces

Syntax Description

Default

None

Command Mode

Interface configuration

Usage Guidelines

This command first appeared in Cisco IOS Release 10.0.

Only one list can be assigned per interface. Priority output queueing provides a mechanism to prioritize packets transmitted on an interface.

Use the show queuing priority and show interface commands to display the current status of the output queues.

Example

The following example causes packets on serial interface 0 to be classified by priority list 1:

interface serial 0
 priority-group 1

Related Commands

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Syntax Description

Default

The normal queue, if you use the no form of the command.

Command Mode

Global configuration

Usage Guidelines

This command first appeared in Cisco IOS Release 10.0.

When using multiple rules, remember that the system reads the priority settings in order of appearance. When classifying a packet, the system searches the list of rules specified by priority-list commands for a matching protocol or interface type. When a match is found, the packet is assigned to the appropriate queue. The list is searched in the order it is specified, and the first matching rule terminates the search.

Example

priority-list 1 default low

Related Commands

You can use the master indexes or search online to find documentation of related commands.

Syntax Description

Default

No queuing priorities are established.

Command Mode

Global configuration

Usage Guidelines

This command first appeared in Cisco IOS Release 10.0.

When using multiple rules, remember that the system reads the priority settings in order of appearance. When classifying a packet, the system searches the list of rules specified by priority-list commands for a matching protocol or interface type. When a match is found, the packet is assigned to the appropriate queue. The list is searched in the order it is specified, and the first matching rule terminates the search.

Example

The following example sets any packet type entering on Ethernet interface 0 to a medium priority:

priority-list 3 interface ethernet 0 medium

Related Commands

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Syntax Description

Default

No queuing priorities are established.

Command Mode

Global configuration

Usage Guidelines

This command first appeared in Cisco IOS Release 10.0.

When using multiple rules for a single protocol, remember that the system reads the priority settings in order of appearance. When classifying a packet, the system searches the list of rules specified by priority-list commands for a matching protocol type. When a match is found, the packet is assigned to the appropriate queue. The list is searched in the order it is specified, and the first matching rule terminates the search.

The decnet_router-l1 keyword refers to the multicast address for all level-1 routers, which are intra-area routers, and the decnet_router-l2 keyword refers to all level 2 routers, which are interarea routers.

The dlsw, rsrb, and stun keywords refer only to direct encapsulation.

Syntax Description

Default

Command Mode

Global configuration

Usage Guidelines

This command first appeared in Cisco IOS Release 10.0.

If a priority queue overflows, excess packets are discarded and quench messages can be sent, if appropriate, for the protocol.

Example

The following example sets the maximum packets in the priority queue to 10:

priority-list 2 queue-limit 10 40 60 80

Related Commands

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Examples

The following example assigns 1 as the custom queue list, specifies DECnet as the protocol type, and assigns 3 as a queue number to the packets transmitted on this interface:

queue-list 1 protocol decnet 3
 

The following example assigns DECnet packets with a size greater than 200 bytes to queue number 2:

queue-list 2 protocol decnet 2 gt 200
 

The following example assigns DECnet packets with a size less than 200 bytes to queue number 2:

queue-list 4 protocol decnet 2 lt 200
 

The following example assigns traffic that matches IP access list 10 to queue number 1:

queue-list 1 protocol ip 1 list 10
 

The following example assigns Telnet packets to queue number 2:

queue-list 4 protocol ip 2 tcp 23
 

The following example assigns UDP Domain Name service packets to queue number 2:

queue-list 4 protocol ip 2 udp 53
 

The following example assigns traffic that matches Ethernet type code access list 201 to queue number 1:

queue-list 1 protocol bridge 1 list 201

Related Commands

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Syntax Description

Default

20 entries

Command Mode

Global configuration

Usage Guidelines

This command first appeared in Cisco IOS Release 10.0.

Example

In the following example, the queue length of queue 10 is increased to 40:

queue-list 5 queue 10 limit 40

Related Commands

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Syntax Description

Default

Random early detection is disabled.

Command Mode

Interface configuration

Usage Guidelines

This command first appeared in Cisco IOS Release 11.2.

Cisco recommends using the default value for the exponential weighting constant; however, you may need to change this value depending on your operational environment. For example, a value of 10 (the default), which might achieve a loss rate of 10^-4, is recommended for high-speed links such as DS3 and OC3, whereas a value of 7, which might achieve a loss rate of 10^-3, is recommended for T1 links.

Random early detection cannot be configured on an interface already configured with custom, priority, or fair queueing.

Example

The following example enables random early detection on a serial interface:

interface serial 0
random-detect

Related Commands

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Syntax Description

Default

Approximately 5 percent of the CPU is available for process tasks.

Command Mode

Global configuration

Usage Guidelines

This command first appeared in Cisco IOS Release 11.2.

This command applies to the Cisco 7200 series and Cisco 7500 series.

Caution Cisco recommends that you do not change the default values.

Example

The following example makes 20 percent of the CPU available for process tasks:

scheduler allocate 2000 500
 

Related Commands

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Syntax Description

Default

High-priority operations are allowed to use as much of the central processor as needed.

Command Mode

Global configuration

Usage Guidelines

This command first appeared in Cisco IOS Release 10.0.

The normal operation of the network server allows the switching operations to use as much of the central processor as is required. If the network is running unusually heavy loads that do not allow the processor the time to handle the routing protocols, give priority to the system process scheduler. High-priority operations are allowed to use as much of the central processor as needed.

On the Cisco 7200 series and Cisco 7500 series, use the scheduler allocate global configuration command.

Example

The following example changes the low-priority process schedule to an interval of 750 milliseconds:

scheduler interval 750
 

Related Commands

You can use the master indexes or search online to find documentation of related commands.

Syntax Description

This command has no arguments or keywords.

Default

Disabled

Command Mode

Global configuration

Usage Guidelines

This command first appeared in Cisco IOS Release 10.0.

When using a standard TCP implementation to send keystrokes between machines, TCP tends to send one packet for each keystroke typed. On larger networks, many small packets use up bandwidth and contribute to congestion.

John Nagle's algorithm (RFC 896) helps alleviate the small-packet problem in TCP. In general, it works this way: The first character typed after connection establishment is sent in a single packet, but TCP holds any additional characters typed until the receiver acknowledges the previous packet. Then the second, larger packet is sent, and additional typed characters are saved until the acknowledgment comes back. The effect is to accumulate characters into larger chunks, and pace them out to the network at a rate matching the round-trip time of the given connection. This method is usually a good for all TCP-based traffic. However, do not use the service nagle command if you have XRemote users on X Window sessions.

Example

The following example enables the Nagle algorithm:

service nagle

Syntax Description

Command Mode

EXEC

Default

The show buffers command without any arguments displays all buffer pool information.

Usage Guidelines

This command first appeared in Cisco IOS Release 10.0.

Sample Displays

The following is sample output from the show buffers command with no arguments, showing all buffer pool information:

Router# show buffers
 
Buffer elements:
     398 in free list (500 max allowed)
     1266 hits, 0 misses, 0 created
 
Public buffer pools:
Small buffers, 104 bytes (total 50, permanent 50):
     50 in free list (20 min, 150 max allowed)
     551 hits, 0 misses, 0 trims, 0 created
Middle buffers, 600 bytes (total 25, permanent 25):
     25 in free list (10 min, 150 max allowed)
     39 hits, 0 misses, 0 trims, 0 created
Big buffers, 1524 bytes (total 50, permanent 50):
     49 in free list (5 min, 150 max allowed)
     27 hits, 0 misses, 0 trims, 0 created
VeryBig buffers, 4520 bytes (total 10, permanent 10):
     10 in free list (0 min, 100 max allowed)
     0 hits, 0 misses, 0 trims, 0 created
Large buffers, 5024 bytes (total 0, permanent 0):
     0 in free list (0 min, 10 max allowed)
     0 hits, 0 misses, 0 trims, 0 created
Huge buffers, 18024 bytes (total 0, permanent 0):
     0 in free list (0 min, 4 max allowed)
     0 hits, 0 misses, 0 trims, 0 created
          
Interface buffer pools:
Ethernet0 buffers, 1524 bytes (total 64, permanent 64):
     16 in free list (0 min, 64 max allowed)
     48 hits, 0 fallbacks
     16 max cache size, 16 in cache
Ethernet1 buffers, 1524 bytes (total 64, permanent 64):
     16 in free list (0 min, 64 max allowed)
     48 hits, 0 fallbacks
     16 max cache size, 16 in cache
Serial0 buffers, 1524 bytes (total 64, permanent 64):
     16 in free list (0 min, 64 max allowed)
     48 hits, 0 fallbacks
     16 max cache size, 16 in cache
Serial1 buffers, 1524 bytes (total 64, permanent 64):
     16 in free list (0 min, 64 max allowed)
     48 hits, 0 fallbacks
     16 max cache size, 16 in cache
TokenRing0 buffers, 4516 bytes (total 48, permanent 48):
     0 in free list (0 min, 48 max allowed)
     48 hits, 0 fallbacks
     16 max cache size, 16 in cache
TokenRing1 buffers, 4516 bytes (total 32, permanent 32):
     32 in free list (0 min, 48 max allowed)
     16 hits, 0 fallbacks
 
0 failures (0 no memory)
 

The following is sample output from the show buffers command with an interface type and identifier:

Router# show buffers Ethernet 0
 
Ethernet0 buffers, 1524 bytes (total 64, permanent 64):
     16 in free list (0 min, 64 max allowed)
     48 hits, 0 fallbacks
     16 max cache size, 16 in cache
 

Syntax Description

Default

Fair queueing configuration

Command Mode

Privileged EXEC

Usage Guidelines

This command first appeared in Cisco IOS Release 10.3.

If no keyword is entered, this command show the status of fair queueing configuration.

Sample Displays

The following is sample output from the show queueing custom EXEC command:

Router# show queueing custom
 
Current custom queue configuration:
 
List   Queue  Args
3      10     default
3      3      interface Tunnel3
3      3      protocol ip
3      3      byte-count 444 limit 3 
 

The following is sample output from the show queueing command. On interface Serial0, there are two active conversations. Weighted fair queueing ensures that both of these IP data streams--both using TCP--receive equal bandwidth on the interface while they have messages in the pipeline, even though there is more FTP data in the queue than rcp data.

Router# show queueing 
 
Current fair queue configuration:
Interface Serial0
  Input queue: 0/75/0 (size/max/drops); Total output drops: 0
  Output queue: 18/64/30 (size/threshold/drops)
     Conversations 2/8 (active/max active)
     Reserved Conversations 0/0 (allocated/max allocated)
 
  (depth/weight/discards) 3/4096/30
  Conversation 117, linktype: ip, length: 556, flags: 0x280
  source: 172.31.128.115, destination: 172.31.58.89, id: 0x1069, ttl: 59,
  TOS: 0 prot: 6, source port 514, destination port 1022
 
  (depth/weight/discards) 14/4096/0
  Conversation 155, linktype: ip, length: 1504, flags: 0x280
  source: 172.31.128.115, destination: 172.31.58.89, id: 0x104D, ttl: 59, 
  TOS: 0 prot: 6, source port 20, destination port 1554

Related Commands

You can use the master indexes or search online to find documentation of related commands.

Syntax Description

Command Mode

EXEC

Usage Guidelines

This command first appeared in Cisco IOS Release 11.2.

Related Commands

You can use the master indexes or search online to find documentation of related commands.

Syntax Description

Command Mode

EXEC

Usage Guidelines

This command first appeared in Cisco IOS Release 11.2.

Related Commands

You can use the master indexes or search online to find documentation of related commands.

Syntax Description

Default

No available bandwidth is estimated when BECNs are received.

Command Mode

Interface configuration

Usage Guidelines

This command first appeared in Cisco IOS Release 11.2.

The bit rate specified for the traffic-shape rate command is the upper limit, and the bit rate specified for the traffic-shape adaptive command is the lower limit to which traffic is shaped when BECNs are received on the interface. The rate actually shaped to will be between these two rates. The traffic-shape adaptive command should be configured at both ends of the link, as it also configures the device at the flow end to reflect forward explicit congestion notification (FECN) signals as BECNs, enabling the router at the high-speed end to detect and adapt to congestion even when traffic is flowing primarily in one direction.

Example

The following example configures traffic shaping on interface 0.1 with an upper limit of 128 kbps and a lower limit of 64 kbps. This allows the link to run from 64 to 128 kbps, depending on the congestion level.

interface serial 0
 encapsulation-frame-relay
interface serial 0.1
 traffic-shape rate 128000
 traffic-shape adaptive 64000

Related Commands

You can use the master indexes or search online to find documentation of related commands.

Syntax Description

This command has no arguments or keywords.

Defaults

Traffic shaping is disabled.

Command Modes

Interface configuration

Usage Guidelines

This command first appeared in Cisco IOS Release 11.2.

Enable traffic shaping on the interface with the traffic-shape rate or traffic-shape group command. FECN is available only when traffic shaping is configured.

Syntax Description

Default

Traffic shaping is disabled.

Command Mode

Interface configuration

Usage Guidelines

This command first appeared in Cisco IOS Release 11.2.

The traffic-shape group command allows you to specify one or more previously defined access list to shape traffic to on the interface. You must specify one traffic-shape group command for each access list on the interface.

You would use traffic shaping if you have a network with differing access rates or if you are offering a subrate service. You can configure the values according to your contract with your service provider or service levels you intend to maintain.

An interval is calculated as follows:

• If the burst-size is not equal to zero, the interval is the burst-size divided by the bit-rate.

• If the burst-size is zero, the interval is the excess-burst-size divided by the bit-rate.

If traffic shaping is performed on a Frame Relay network with the traffic-shape rate command, you can also use the traffic-shape adaptive command to specify the minimum bit-rate the traffic is shaped to.

Example

The following example enables traffic that matches access list 101 to be shaped to a certain rate and traffic matching access list 102 to be shaped to another rate on the interface:

interface serial 1 
 traffic-shape rate 128000 16000 8000 group 101
 traffic-shape rate 130000 10000 1000 group 102

Related Commands

You can use the master indexes or search online to find documentation of related commands.

Syntax Description

Default

Traffic shaping is disabled.

Command Mode

Interface configuration

Usage Guidelines

This command first appeared in Cisco IOS Release 11.2.

You would use traffic shaping if you have a network with differing access rates or if you are offering a subrate service. You can configure the values according to your contract with your service provider or service levels you intend to maintain.

An interval is calculated as follows:

• If the burst-size is not equal to zero, the interval is the burst-size divided by the bit-rate.

• If the burst-size is zero, the interval is the excess-burst-size divided by the bit-rate.

If traffic shaping is performed on a Frame Relay network with the traffic-shape rate command, you can also use the traffic-shape adaptive command to specify the minimum bit-rate the traffic is shaped to.

Example

The following example enables traffic shaping on a serial interface using the bandwidth required by the service provider:

interface serial 0
 traffic-shape rate 128000 16000 8000

Related Commands

You can use the master indexes or search online to find documentation of related commands.