Browsing articles in "Tutorial"
Dec
17
2010
Send email from your router using EEM
Send-email-from-your-router-using-EEM

Cisco IOS Embedded Event Manager (EEM) is a powerful and flexible subsystem that provides real-time network event detection and onboard automation. It gives you the ability to adapt the behavior of your network devices to align with your business needs. Customers can use EEM to create and run programs or scripts directly on a router or switch. The scripts are referred to as EEM Policies and can be programmed using a simpleCLI-based interface or using a scripting language called Tool Command Language (TCL). EEM allows customers to harness the significant intelligence within Cisco IOS Softwareto respond to real-time events, automate […]

Dec
7
2010
Access to the console via AUX port
rollover_cable

Often in a network environment, it is needed to manage a router/switch via console, but what can you do if you don’t have a computer with a serial interface? You can use another router! It is easy to do it. 1) Connect the console interface of the router/switch to the router aux interface using a rollover cable. Rollover cables essentially have one end of the cable wired exactly opposite from the other. As you can see below, this essentially “rolls over” the wires.

Nov
22
2010
Cron? no Kron :)
Cron-no-Kron

Cron is a time-based job scheduler in Unix-like computer operating systems. The name cron comes from the word “chronos”, Greek for “time”. Cron enables users to schedule jobs (commands or shell scripts) to run periodically at certain times or dates. It is commonly used to automate system maintenance or administration, though its general-purpose nature means that it can be used for other purposes, such as connecting to the Internet and downloading email. What can I use to schedule a script or a command in Cisco? The kron feature :) Kron provides the ability to schedule some EXEC command-line interface (CLI) […]

Nov
5
2010
The break key sequence in the password recovery
The-break-key-sequence-in-the-password-recovery

What can I do if I forgot the password in my router? The fastest solution is replace it with the ‘password recovery‘ (you can try to find the password with bruteforce attack but I think it is not the better solution..). During the password recovery procedure, it is fundamental sent the correct ‘Break’ key sequence to enable ROMMON, but, as you know, the ‘break’ sequence depends by the software that you use! Below the standard break key sequence combinations for the most common operating systems.

Oct
6
2010
Using regular expressions with the ‘Show’ command
Using-regular-expressions-with-the-Show-command

Do you remember the “Cisco regular expressions” tutorial? A regular expression is entered as part of a command and is a pattern made up of symbols, letters, and numbers that represent an input string for matching (or sometimes not matching). Matching the string to the specified pattern is called pattern matching. Pattern matching either succeeds or fails. If a regular expression can match two different parts of an input string, it will match the earliest part first. In this tutorial, I will explain how to use the ‘show’ command with the regular expression.

Sep
29
2010
Cisco regular expressions
Using-regular-expressions-with-the-Show-command

The origins of regular expressions lie in automata theory and formal language theory, both of which are part of theoretical computer science. These fields study models of computation (automata) and ways to describe and classify formal languages. In the 1950s, mathematician Stephen Cole Kleene described these models using his mathematical notation called regular sets. The SNOBOL language was an early implementation of pattern matching, but not identical to regular expressions. Ken Thompson built Kleene’s notation into the editor QED as a means to match patterns in text files. A regular expression is entered as part of a command and is […]

Sep
20
2010
Cisco IOS Keyboard Shortcuts
Cisco-IOS-Keyboard-Shortcuts

A number of shortcuts exist within the IOS command line interface. The most famous shortcut is the ‘TAB’ command, that completes a partially typed CLI command. For istance, if you type “sh ru” and press TAB, it will complete the command as “show running-config“. Below the complete list of the IOS shortcuts: Ctrl+T: Swap the current character with the one before it Ctrl+K: Erase all characters from the current cursor position to the end of the line Ctrl+X: Erase all characters from the current cursor position to the beginning of the line Ctrl+L: Reprint the line Ctrl+C: Exit configuration mode

Jul
13
2010
Hub & Spoke: an example of VRF-Lite
vrf-lite-virtual-connection

VRF is an extension of IP routing that provides multiple routing instances. It provides a separate IP routing and forwarding table to each VPN and is used in concert with MP-iBGP (Multi-Protocol internal BGP) between provider equipment (PE) routers to provide Layer 3 MPLS-VPN. However, ML-Series VRF implementation is without MP-iBGP. With VRF Lite, the ML Series is considered a PE-extension or a customer equipment (CE)-extension. VRF Lite is considered a PE-extension since its has VRF (but without MP-iBGP), and it is considered a CE-extension since this CE can have multiple VRFs and serves many customer with one CE box. […]

Mar
12
2010
Smartports Macros: a useful command

Working in a datacenter, it is often required to apply the same intereface configuration on many ports; Cisco has an embedded useful command to do it: the smartports macros. Smartports macros provide a convenient way to save and share common configurations. You can use Smartports macros to enable features and settings based on the location of a switch in the network and for mass configuration deployments across the network. Each Smartports macro is a set of CLI commands that you define. Smartports macros do not contain new CLI commands; they are simply a group of existing CLI commands. When you apply a […]

Jan
8
2010
How to use archive command to save configuration

In a large/critical network, it is fundamental backup the Cisco configuration for two reasons: Rollback configuration Restore configuration in case of a broken router There are two ways to backup: manually (using write command each time that you would save running configuration) or automatically (using software like Ciscoworks, HP OpenView, … ). In this tutorial, I would explain a different method to backup configuration: the archive command. Introduced into Cisco IOS Release 12.3(4)T, the archive command permits to save a copy of the current running configuration to different path: ftp, http, https, rcp, scp, tftp servers. Moreover the archive command has […]