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 [...]

Recently, I have upgraded my Cisco 2650XM from 12.3 to 12.4 version; I use it to connect my PC to Internet, but something goes wrong.
After the upgrading, I have tried to downlad an ISO image but the speed was very low (about 300KB/s and not 700KB/s). Mhhh this is strange! I have begun the troubleshooting [...]

Cisco Network Foundation Protection (NFP) is an umbrella strategy encompassing Cisco IOS Security features that provides the tools, technologies, and services that enable organizations to secure their network foundations. NFP helps to establish a methodical approach to protecting router planes, forming the foundation for continuous service delivery.
The router is typically segmented into three planes of [...]

The Open Shortest Path First (OSPF) protocol, defined in RFC 2328, is an Interior Gateway Protocol used to distribute routing information within a single Autonomous System.
The OSPF protocol is based on link-state technology, which is a departure from the Bellman-Ford vector based algorithms used in traditional Internet routing protocols such as RIP. OSPF has introduced [...]

It is not common see a Cisco crash: Software forced crash, Bus Error, Software watchdog timeout, and so on…
But if you would do it, there is a pretty trick : it’s the “test crash” command, an hidden IOS command. This can help you if you are lucky enough to have the real crash [...]

In this article I would explain some tips for securing Cisco administrative access.
When creating passwords, keep these rules in mind:

Make passwords lengthy
Passwords should combine letters, numbers, and symbols. Passwords should not use dictionary words
Change passwords as often as possible

Strong passwords are the primary defense against unauthorized access to your router. The best way to manage [...]

The spanning-tree protocol is used to cut loops that redundant links create in bridge networks. These packets are not attested by the system, so an attacker could spoof the BPDU and compromise the network stability!
See below to understand BPDU attack:
In this example the Ciscozine1 switch is elected Root Bridge due to the lower MAC-address (suppose that [...]

In a typical MAC flooding attack, a switch is flooded with packets, each containing different source MAC addresses. The intention is to consume the limited memory set aside in the switch to store the MAC address-to-physical port translation table.
The result of this attack causes the switch to enter a state called failopen mode, in which [...]

Discovered during Cisco CCNP course, Tcl (originally from “Tool Command Language“) is a scripting language created by John Ousterhout and introduced from IOS version 12.3(2)T.
But what is Cisco Tcl?
The Cisco IOS Tcl shell was designed to allow customers to run Tcl commands directly from the Cisco IOS CLI prompt. Cisco IOS software does contain some [...]

EtherChannel bundles individual Ethernet links into a single logical link that provides bandwidth up to 1600 Mbps (Fast EtherChannel, full duplex) or 16 Gbps (Gigabit EtherChannel) between two Cisco Catalyst switches. All interfaces in each EtherChannel must be the same speed and duplex, and both ends of the channel must be configured as either a [...]