The Switched Port Analyzer (SPAN) feature, which is sometimes called port mirroring or port monitoring, selects network traffic, from a switched port, for analysis by a network analyzer. Unfotunately this feature works only on switches or switches Layer3. And in a router, what can I do to copy the traffic? In a previous article, I explained the Embedded Packet Capture, a powerful feature to capture data packets directly on the NVRAM. Another good solution is the ‘IP traffic export‘. Introduced in 12.3(4)T IOS, the IP Traffic Export feature allows users to configure their router to export IP packets that are [...]

Started with IOS 12.4(20)T version, EPC or Embedded Packet Capture, is a powerful feature to capture data packets flowing through, to, and from, a Cisco router. In contrast with SPAN feature, EPC permits to save the dump directly on the NVRAM and for this reason, Embedded Packet Capture is useful whenever a network protocol analyzer might be useful in debugging a problem, but when it’s not practical to install such a device. The features are: The ability to capture IPv4 and IPv6 packets in the Cisco Express Forwarding path A flexible method for specifying the capture buffer size and type [...]

How long does it take to reload your router? 3 or 4 minutes? Do you know that is possible to speed up your reboot? If your answer is negative, read how warm reload is faster than cold (classic) reload. Introduced in Cisco IOS Release 12.3(2)T, the warm reload feature allows users to reload their routers without reading images from storage. That is, the Cisco IOS image reboots without ROM monitor mode (ROMMON) intervention by restoring the read-write data from a previously saved copy in the RAM and by starting execution without either copying the image from flash to RAM or [...]

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 [...]

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) commands [...]

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.

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 [...]

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.  [...]

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 [...]

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 [...]