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Cisco Services & Technologies

How to Fix Cisco VPN Client Error 51 – Unable to…

Apple Mac OS X users are frequently faced with the Cisco VPN Client Error 51 - Unable to Communicate with the VPN Subsystem as shown in the screenshot below: When this error is produced, users wil…

Spanning Tree Protocol (STP)

Spanning Tree Protocol – Part 2: Rapid STP Port C…

Spanning Tree Protocol, Rapid STP port costs and port states are an essential part of the STP algorithm that affect how STP decides to forward or block a port leading to the Root Bridge. In our prev…

Spanning Tree Protocol (STP)

Spanning Tree Protocol – Part 3: Bridge ID, Prior…

In this article we will examine the Spanning Tree Bridge ID structure, explain why it has increments of 4096, how VLAN information is embedded (for Per-VLAN Spanning Tree & multiple STP instances…

Routing

OSPF - Part 6: OSPF LSA Types - Purpose and Funct…

Our previous article explained the purpose of Link State Update (LSU) packets and examined the Link State Advertisement (LSA) information contained within LSU packets. We also saw the most common LSA…

Cisco Routers

Configuring Site to Site IPSec VPN Tunnel Between…

Site-to-Site IPSec VPN Tunnels are used to allow the secure transmission of data, voice and video between two sites (e.g offices or branches). The VPN tunnel is created over the Internet public netwo…

Cisco Routers

Installing Security Device Manager (SDM) on a Cis…

For years now, Cisco has been developing its Security Device Manager (SDM) software. This web-based software is designed to help the less experienced users and administrators to work and configure va…

Cisco Data Center (Nexus/UCS)

The Complete Cisco Nexus vPC Guide. Features & Ad…

Cisco virtual Port Channel (vPC) is a virtualization technology, launched in 2009, which allows links that are physically connected to two different Cisco Nexus Series devices to appear as a single p…

Network Protocols

Introduction To Protocols

In the networking and communications area, a protocol is the formal specification that defines the procedures that must be followed when transmitting or receiving data. Protocols define the format, t…

Linux - Unix

Finding More Information On The Linux Operating S…

Since this document merely scratches the surface when it comes to Linux, you will probably find you have lots of questions and possibly problems. Whether these are problems with the operating system…

Cisco Data Center (Nexus/UCS)

Complete Guide to Nexus Checkpoint & Rollback Fea…

The Cisco NX-OS checkpoint feature provides the capability to capture at any time a snapshot (backup) of the Cisco Nexus configuration before making any changes. The captured configura…

Routing

Link State Routing Protocols

Link State routing protocols do not view networks in terms of adjacent routers and hop counts, but they build a comprehensive view of the overall network which fully describes the all possible routes…

Cisco Routers

Cisco Type 7 Password Decrypt / Decoder / Crack T…

The Firewall.cx Cisco Password Decoder Tool (see below) provides readers with the ability to decrypt 'Type 7' cisco passwords. For security reasons, we do not keep any history of decoded passwords…