Cisco router tutorials

Set the telnet source IP address for a Cisco router

Contributed by qmchenry on June 18, 2006 under Cisco router

The default source IP address when telnetting from a Cisco router is that of the interface closest to the destination. Because some access lists may block traffic from the default IP address, or to help test access lists, it may be useful to temporarily or permanently set the telnet source IP address.

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Send messages to other users on a Cisco Router

Contributed by qmchenry on under Cisco router

Multiple users can be logged into a Cisco router at the same time. It may be necessary (or sometimes just fun) to send a text message to one or all users on a router. For example, if you are preparing to reload the router, admin etiquette dictates that you should warn other users.

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Show or list which users are logged into a Cisco router

Contributed by qmchenry on under Cisco router

Wide area networks are often very wide and installing or troubleshooting remote routers often requires fingers on keyboards in more than one physical location. It is simple to get a listing of the users logged into a router which makes it easier to send that user a message (as many remote locations have no cell phone signal).

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Configure Cisco router to send messages to remote syslog server

Contributed by qmchenry on June 13, 2006 under Cisco router

Centralizing log messages to a syslog server can improve the managability of any size network and can decrease response times to resolve problems. Sending router log messages to a remote server also allows longer archiving of messages than in a router’s limited storage. Messages stored by syslog have permanence that a router doesn’t. When a router is reloaded or power cycled, the messges in its log are erased. This recipe describes the configuration steps required to make a router send messages to a remote syslog server.

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Clear or erase Cisco router log

Contributed by qmchenry on under Cisco router

A router’s log can save your life. Well, at the least it can save you time and headaches when troubleshooting problems. However, in the heat of battle, in the actual hotness of the battle, old messages in the log can get in the way. After making a change to the router’s configuration, for instance, it is easier to monitor only subsequent messages in the log. Clearing the log is a snap.

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Increase or change Cisco router log size

Contributed by qmchenry on under Cisco router

Messages logged by a router can make troubleshooting problems substantially easier. However, the default size of most Cisco routers is 4096 bytes which typically accomodates fewer than 60 messages. While this may help in many situations, adding some additional space can save the day when a router generates frequent error messages as when an interface state cycles up and down. This recipe describes the simple configuration to increase the size of the router log.

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Copy Cisco router config into flash to backup or replace hardware

Contributed by qmchenry on June 12, 2006 under Cisco router

When replacing a faulty router that is not completely dead, it may be possible to copy the startup configuration to the removable flash memory and swap the flash to get the new router up and configured in as short a time as possible. Without this procedure, it will be necessary to manually copy the old configuration to the new router. This simple command also provides a local backup copy of the router’s config which can save hours of work when replacing a dead router.

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Assign or configure IP addresses on Cisco routers

Contributed by qmchenry on May 25, 2006 under Cisco router

Every active interface on a Cisco router to be used with IP requires an IP address assigned to it. This short recipe describes how to set an interface’s IP address.

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