Performing Basic System Management

Last Updated: October 10, 2011

This module describes the basic tasks that you can perform to manage the general system features of the Cisco IOS software--those features that are generally not specific to a particular protocol.

Finding Feature Information

Your software release may not support all the features documented in this module. For the latest feature information and caveats, see the release notes for your platform and software release. To find information about the features documented in this module, and to see a list of the releases in which each feature is supported, see the Feature Information Table at the end of this document.

Use Cisco Feature Navigator to find information about platform support and Cisco software image support. To access Cisco Feature Navigator, go to www.cisco.com/go/cfn. An account on Cisco.com is not required.

Information About Performing Basic System Management

System Name

The system name, also called the hostname, is used to uniquely identify the system in your network. The system name is displayed at the CLI prompt. If no name is configured, the system default name is Router.

Command Aliases

Command aliases allow you to configure alternative syntax for commands. You may want to create aliases for commonly used or complex commands. For example, you could assign the alias save config to the copy running-config startup-config command to reduce the amount of typing you have to perform, or if your users might find the save config command easier to remember. Use word substitutions or abbreviations to tailor the command syntax for you and your user community.

Remember that any aliases you configure will be effective only on your system, and that the original command syntax will appear in the configuration file.

Minor Services

Minor services are small servers that run on your routing device and are useful for basic system testing and for providing basic network functions. Minor services are useful for testing connections from another host on the network.

Cisco small servers are conceptually equivalent to daemons.

Small servers provided by Cisco IOS software-based devices include TCP, UDP, HTTP, Bootstrap Protocol (BOOTP), and Finger. For information about the HTTP server, see the "Using the Cisco Web Browser User Interface" chapter in the Cisco IOS Configuration Fundamentals Configuration Guide.

The TCP small server provides the following minor services:

  • Chargen--Generates a stream of ASCII data. To test this service, issue the telnet a.b.c.d chargencommand from a remote host.
  • Daytime--Returns the system date and time if you have configured Network Time Protocol (NTP) or set the date and time manually. To test this service, issue the telnet a.b.c.d daytimecommand from a remote host.
  • Discard--Discards whatever you type. To test this service, issue the telnet a.b.c.d discardcommand from a remote host.
  • Echo--Echoes back whatever you type. To test this service, issue the telnet a.b.c.d echocommand from a remote host.

The UDP small server provides the following minor services:

  • Chargen--Discards the datagram that you send and responds with a 72-character string of ASCII characters terminated with a CR+LF (carriage return and line feed).
  • Discard--Discards the datagram you send.
  • Echo--Echoes the payload of the datagram that you send.

Minor services are disabled by default.


Caution

Enabling minor services creates the potential for certain types of denial-of-service (DoS) attacks, such as the UDP diagnostic port attack. Therefore, any network device that has UDP, TCP, BOOTP, or Finger services should be protected by a firewall or have the minor services disabled. For information on preventing UDP diagnostic port attacks, see the white paper titled Defining Strategies to Protect Against UDP Diagnostic Port Denial of Service Attacks a vailable on Cisco.com.

BOOTP Server

You can enable or disable an async line Bootstrap Protocol (BOOTP) service on your routing device. This small server is enabled by default. Due to security considerations, this service should be disabled if you are not using it.

Because DHCP is based on the BOOTP, both of these service share the well-known UDP server port 67 (per the Internet standards and RFCs). For more information about DHCP configuration in the Cisco IOS software, see the Cisco IOS IP Addressing Configuration Guide. For more information about BOOTP, see RFC 951. Interoperation between BOOTP and DHCP is defined in RFC 1534. DHCP is defined in RFC 2131.

Finger Protocol

The Finger protocol allows users throughout the network to get a list of the users currently using a particular routing device. The information displayed includes the processes running on the system, the line number, connection name, idle time, and terminal location. This information is provided through the Cisco IOS software show users EXEC command.

Hidden Telnet Addresses

You can hide addresses while attempting to establish a Telnet session. The hide feature suppresses the display of the address and continues to display all other messages that normally would be displayed during a connection attempt, such as detailed error messages if the connection fails.

EXEC Startup Delay

To delay the startup of the EXEC process on noisy lines until the line has been idle for 3 seconds, use the service exec-wait command in global configuration mode.

This command is useful on noisy modem lines or when a modem attached to the line is configured to ignore Microcom Networking Protocol (MNP) or V.42 negotiations, and when MNP or V.42 modems are dialing in. In these cases, noise or MNP/V.42 packets might be interpreted as usernames and passwords, causing authentication failure before the user can type a username or password. This command is not useful on nonmodem lines or lines without some kind of login configured.

Idle Telnet Connections

Normally, data sent to noncurrent Telnet connections is accepted and discarded. When the service telnet-zero-idle command is enabled and a session is suspended (that is, some other connection is made active), the TCP window is set to zero. This action prevents the remote host from sending any more data until the connection is resumed. Use this command when all messages sent by the host must be seen by the users and the users are likely to use multiple sessions. Do not use this command if your host will eventually time out and log out a TCP user whose window is zero.

Interval for Load Data

You can change the period of time over which a set of data is used for computing load statistics. Decisions, such as dial backup, depend on these statistics. If you decrease the load interval, the average statistics are computed over a shorter period of time and are more responsive to bursts of traffic.

Number of TCP Transactions

When you are using a standard TCP implementation to send keystrokes between machines, TCP tends to send one packet for each keystroke typed, which can use up the bandwidth and contribute to the congestion on larger networks.

John Nagle's algorithm (RFC 896) helps alleviate the small-packet problem in TCP. The first character typed after the connection establishment is sent in a single packet, but TCP holds any additional characters that are typed until the receiver acknowledges the previous packet. Then the second, larger packet is sent, and the additional typed characters are saved until the acknowledgment comes back. The effect is to accumulate characters into larger chunks, and pace their transmission to the network at a rate matching the round-trip time of the given connection. This method is usually preferable for all TCP-based traffic.

By default, the Nagle algorithm is not enabled.

Switching and Scheduling Priorities

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

System Buffer Size

You can adjust the initial buffer pool settings and limits at which temporary buffers are created and destroyed.

During normal system operation, there are two sets of buffer pools: public and interface. They behave as follows:

  • The buffers in the public pools grow and shrink based upon demand. Some public pools are temporary and are created and destroyed as needed. Other public pools are permanently allocated and cannot be destroyed. Public buffer pools are labeled as small, middle, big, very big, large, and huge.
  • Interface pools are static--that is, they are all permanent. One interface pool exists for each interface. For example, a Cisco 4000 1E 4T configuration has one Ethernet buffer pool and four serial buffer pools.

The server has one pool of queueing elements and six public pools of packet buffers of different sizes. For each pool, the server keeps count of the number of outstanding buffers, the number of buffers in the free list, and the maximum number of buffers allowed in the free list.

How to Perform Basic System Management

Setting Basic System Parameters

To set basic system parameters perform the following steps. You can perform these steps based on the customization requirements of your system.

SUMMARY STEPS

1.    hostname name

2.    prompt string

3.    alias mode alias-name alias-command-line

4.    service tcp-small-servers

5.    service udp-small-servers

6.    no ip bootp server

7.    ip finger

8.    ip finger rfc-compliant

9.    service hide-telnet-address

10.    line line-number

11.    busy-message

12.    exit

13.    service exec-wait

14.    service telnet-zero-idle

15.    load-interval seconds

16.    service nagle

17.    scheduler interval milliseconds

18.    scheduler allocate [network-microseconds process-microseconds]

19.    scheduler process-watchdog {hang | normal | reload | terminate}

20.    buffers {small | middle | big | verybig | large | huge | type number} {permanent | max-free | min-free | initial} number

21.    exit

22.    show aliases [mode]

23.    show buffers


DETAILED STEPS
Step 1   hostname name

Use the hostname name command to perform the basic system management task of assigning a name for your device.



Example: 
Router(config)# hostname host1
Step 2   prompt string

or

no service prompt config

By default, the CLI prompt consists of the system name followed by an angle bracket (>) for user EXEC mode or a pound sign (#) for privileged EXEC mode. Use the the prompt string or the no service prompt config command to customize the CLI prompt for your system.



Example: 
Router(config)# prompt Router123

or



Example: 
Router(config)# no service prompt config
Step 3   alias mode alias-name alias-command-line

Use the alias mode alias-name alias-command-line command to create a command alias.



Example: 
Router(config)# alias exec save config copy running-config startup-config
Step 4   service tcp-small-servers

Use the service tcp-small-servers command to enable minor TCP services such as chargen, daytime, discard, and echo.

Note    The no form of the service tcp-small-servers command will appear in the configuration file when these basic services are disabled.


Example: 
Router(config)# service tcp-small-servers
Step 5   service udp-small-servers

Use the service udp-small-servers command to enable minor UDP services such as chargen, daytime, discard, and echo.

Note    The no form of the service udp-small-servers command will appear in the configuration file when these basic services are disabled.


Example: 
Router(config)# service udp-small-servers
Step 6   no ip bootp server

Use the no ip bootp server command to disable the BOOTP server on your platform.



Example: 
Router(config)# no ip bootp server
Step 7   ip finger

Use the ip finger command to enable a Cisco device to respond to Finger (port 79) requests. When the ip finger command is configured, the router will respond to a telnet a.b.c.d finger command from a remote host by immediately displaying the output of the show userscommand and then closing the connection.



Example: 
Router(config)# ip finger
Step 8   ip finger rfc-compliant

Use the ip finger rfc-compliant command to configure the finger protocol to be compliant with RFC 1288. The ip finger rfc-compliant command should not be configured for devices with more than 20 simultaneous users. When the ip finger rfc-compliantcommand is configured, the router will wait for input before displaying any information. The remote user can then press the Return key to display the output of the show users command, or enter /W to display the output of the show users wide command. After this information is displayed, the connection is closed.



Example: 
Router(config)# ip finger rfc-compliant
Step 9   service hide-telnet-address

Use the service hide-telnet-address command to configure the router to suppress Telnet addresses.



Example: 
Router(config)# service hide-telnet-address
Step 10   line line-number

Use the line command to enter line configuration mode.



Example: 
Router(config)# line 1
Step 11   busy-message

Use the busy-message command with the service hide-telnet-addresscommand to customize the information displayed during Telnet connection attempts. If the connection attempt fails, the router suppresses the address and displays the message specified with the busy-message command.



Example: 
Router(config-line)# busy-message
Step 12   exit

Use the exit command to exit line configuration mode and return to global configuration mode.



Example: 
Router(config-line)# exit
Step 13   service exec-wait

Use the service exec-waitcommand to delay the startup of the EXEC process on noisy lines until the line has been idle for 3 seconds.



Example: 
Router(config)# service exec-wait
Step 14   service telnet-zero-idle

Use the service telnet-zero-idle command to configure the Cisco IOS software to set the TCP window to zero (0) when the Telnet connection is idle.



Example: 
Router(config)# service telnet-zero-idle
Step 15   load-interval seconds

Use the load-interval seconds command to change the length of time for which a set of data is used to compute load statistics.



Example: 
Router(config)# load-interval 100
Step 16   service nagle

Use the service nagle command to enable the Nagle algorithm and thereby reduce the number of TCP transactions.



Example: 
Router(config)# load-interval 100
Step 17   scheduler interval milliseconds

Use the scheduler interval milliseconds command to define the maximum amount of time that can elapse without running the lowest-priority system processes.



Example: 
Router(config)# scheduler interval 100
Step 18   scheduler allocate [network-microseconds process-microseconds]

Use the scheduler allocate command to change the amount of time that the CPU spends on fast-switching and process-level operations on the Cisco 7200 series and Cisco 7500 series routers.

Caution   

Cisco recommends that you do not change the default values of the scheduler allocate command.



Example: 
Router(config)# scheduler allocate 5000 200
Step 19   scheduler process-watchdog {hang | normal | reload | terminate}

Use the scheduler process-watchdog {hang | normal | reload | terminate} command to configure the characteristics for a looping process.



Example: 
Router(config)# scheduler process-watchdog hang
Step 20   buffers {small | middle | big | verybig | large | huge | type number} {permanent | max-free | min-free | initial} number

Use the buffers {small | middle | big | verybig | large | huge | type number} {permanent | max-free | min-free | initial} number command to adjust the system buffer size.



Example: 
Router(config)# buffers small permanent 10
Caution   

Cisco does not recommend that you adjust these parameters. Improper settings can adversely impact the system performance.

Step 21   exit

Use the exit command to exit global configuration mode and return to privileged EXEC mode.



Example: 
Router(config)# exit
Step 22   show aliases [mode]

Use the show aliases [mode] command to display a list of command aliases currently configured on your system, and the original command syntax for those aliases.



Example: 
Router# show aliases exec
Step 23   show buffers

Use the show bufferscommand to display buffer information. For more information about this command, see the Cisco IOS Configuration Fundamentals Command Reference.



Example: 
Router# show buffers
Buffer elements:
     1119 in free list (1119 max allowed)
     641606 hits, 0 misses, 619 created
Public buffer pools:
Small buffers, 104 bytes (total 50, permanent 50):
     48 in free list (20 min, 150 max allowed)
     2976557 hits, 0 misses, 0 trims, 0 created
     0 failures (0 no memory)
Middle buffers, 600 bytes (total 25, permanent 25, peak 37 @ 2w0d):
     25 in free list (10 min, 150 max allowed)
     445110 hits, 4 misses, 12 trims, 12 created
     0 failures (0 no memory)
Big buffers, 1536 bytes (total 50, permanent 50):
     50 in free list (5 min, 150 max allowed)
     58004 hits, 0 misses, 0 trims, 0 created
     0 failures (0 no memory)
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
     0 failures (0 no memory)
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
     0 failures (0 no memory)
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
     0 failures (0 no memory)
Interface buffer pools:
Syslog ED Pool buffers, 600 bytes (total 282, permanent 282):
     257 in free list (282 min, 282 max allowed)
     32 hits, 0 misses
IPC buffers, 4096 bytes (total 2, permanent 2):
     1 in free list (1 min, 8 max allowed)
     1 hits, 0 fallbacks, 0 trims, 0 created
     0 failures (0 no memory)
Header pools:
Header buffers, 0 bytes (total 511, permanent 256, peak 511 @ 2w0d):
     255 in free list (256 min, 1024 max allowed)
     171 hits, 85 misses, 0 trims, 255 created
     0 failures (0 no memory)
     256 max cache size, 256 in cache
     0 hits in cache, 0 misses in cache
Particle Clones:
     1024 clones, 0 hits, 0 misses
Public particle pools:
F/S buffers, 128 bytes (total 512, permanent 512):
     0 in free list (0 min, 512 max allowed)
     512 hits, 0 misses, 0 trims, 0 created
     0 failures (0 no memory)
     512 max cache size, 512 in cache
     0 hits in cache, 0 misses in cache
Normal buffers, 512 bytes (total 2048, permanent 2048):
     2048 in free list (1024 min, 4096 max allowed)
     0 hits, 0 misses, 0 trims, 0 created
     0 failures (0 no memory)
Private particle pools:
HQF buffers, 0 bytes (total 2000, permanent 2000):
     2000 in free list (500 min, 2000 max allowed)
     0 hits, 0 misses, 0 trims, 0 created
     0 failures (0 no memory)
Serial2/0 buffers, 512 bytes (total 256, permanent 256):
     0 in free list (0 min, 256 max allowed)
     256 hits, 0 fallbacks
     256 max cache size, 132 in cache
     124 hits in cache, 0 misses in cache
     10 buffer threshold, 0 threshold transitions
Serial2/1 buffers, 512 bytes (total 256, permanent 256):
     0 in free list (0 min, 256 max allowed)
     256 hits, 0 fallbacks
     256 max cache size, 132 in cache
     124 hits in cache, 0 misses in cache
     10 buffer threshold, 0 threshold transitions

Configuration Examples for Performing Basic System Management

There are no configuration examples for the Performing Basic System Management feature.

Additional References

Related Documents

Related Topic

Document Title

Cisco IOS commands

Cisco IOS Master Commands List, All Releases

Network Management commands

Cisco IOS Network Management Command Reference

Cisco IOS fundamental configuration commands

Cisco IOS Configuration Fundamentals Command Reference

Cisco IOS fundamental configurations

Cisco IOS Configuration Fundamentals Configuration Guide

Preventing UDP diagnostic port attacks

Defining Strategies to Protect Against UDP Diagnostic Port Denial of Service Attacks

DHCP configuration

Cisco IOS IP Addressing Configuration Guide

Standards

Standard

Title

None

--

MIBs

MIB

MIBs Link

None

To locate and download MIBs for selected platforms, Cisco software releases, and feature sets, use Cisco MIB Locator found at the following URL:

http://www.cisco.com/go/mibs

RFCs

RFC

Title

RFC 896

Congestion Control in IP/TCP Internetworks

RFC 951

Algorithms for Synchronizing Network Clocks

RFC 1288

The Finger User Information Protocol

RFC 1534

Interoperation Between DHCP and BOOTP

RFC 2131

Dynamic Host Configuration Protocol

Technical Assistance

Description

Link

The Cisco Support and Documentation website provides online resources to download documentation, software, and tools. Use these resources to install and configure the software and to troubleshoot and resolve technical issues with Cisco products and technologies. Access to most tools on the Cisco Support and Documentation website requires a Cisco.com user ID and password.

http://www.cisco.com/cisco/web/support/index.html

Feature Information for Performing Basic System Management

The following table provides release information about the feature or features described in this module. This table lists only the software release that introduced support for a given feature in a given software release train. Unless noted otherwise, subsequent releases of that software release train also support that feature.

Use Cisco Feature Navigator to find information about platform support and Cisco software image support. To access Cisco Feature Navigator, go to www.cisco.com/go/cfn. An account on Cisco.com is not required.

Table 1 Feature Information for Performing Basic System Management

Feature Name

Releases

Feature Information

Performing Basic System Management

10.0

This module describes the basic tasks to manage the general system features of the Cisco IOS software.

Cisco and the Cisco Logo are trademarks of Cisco Systems, Inc. and/or its affiliates in the U.S. and other countries. A listing of Cisco's trademarks can be found at www.cisco.com/go/trademarks. Third party trademarks mentioned are the property of their respective owners. The use of the word partner does not imply a partnership relationship between Cisco and any other company. (1005R)

Any Internet Protocol (IP) addresses and phone numbers used in this document are not intended to be actual addresses and phone numbers. Any examples, command display output, network topology diagrams, and other figures included in the document are shown for illustrative purposes only. Any use of actual IP addresses or phone numbers in illustrative content is unintentional and coincidental.

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