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 [...]

As I explained in the article “Security Device Manager aka SDM“, SDM is a Web-based device-management tool for Cisco routers that can improve the productivity of network managers, simplify router deployments, and help troubleshoot complex network and VPN connectivity issues.
What is a virtual private network?
A virtual private network (VPN) is a computer network 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 [...]

Cisco Router and Security Device Manager (SDM) is a Web-based device-management tool for Cisco routers that can improve the productivity of network managers, simplify router deployments, and help troubleshoot complex network and VPN connectivity issues.
Network and security administrators and channel partners can use Cisco SDM for faster and easier deployment of Cisco routers for integrated [...]

QoS (Quality of Service) involves prioritization of network traffic. QoS is the idea that transmission rates, error rates, and other characteristics can be measured, improved, and, to some extent, guaranteed in advance. QoS can be targeted at a network interface, toward a given server or router’s performance, or in terms of specific applications. A network [...]

Introduced in the Cisco IOS Release 12.2(15), Gateway Load Balancing Protocol (GLBP) is supported by Cisco 1700, 2600, 3620, 3631, 3640, 3660, 3725, 3745, 7100, 7200, 7400, 7500 series. GLBP is a Cisco proprietary protocol that attempts to overcome the limitations of existing redundant router protocols (HSRP, VRRP, …) by adding basic load balancing functionality.
GLBP [...]

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 [...]

As you see in the article “Implementing High Availability with HSRP“, it is quite simple configure Hot Standby Router Protocol.
Some cases require a custom configuration, using priority, track, preempt etc…and these are:

The standby preempt interface configuration command allows the router to become the active router when its priority is higher than all other HSRP-configured routers [...]

The Hot Standby Router Protocol (HSRP) is a Cisco proprietary first-hop redundancy protocol (FHRP) designed to allow for transparent fail-over of the first-hop IP router, and has been described in detail in RFC 2281.
HSRP provides high network availability by providing first-hop routing redundancy for IP hosts on Ethernet, Fiber Distributed Data Interface (FDDI), Bridge-Group Virtual [...]

Cisco IOS permits to define multiple privilege levels for different accounts. This could be useful when many people work on the same router / switch, but with different roles (operator, tecnhician, network manager) and there is no time to implement an authentication server.
There are 16 different privilege levels that can be used. Level 0 is [...]