Configuration Tips

Have you secured your router with an ACL for SNMP access but are still seeing pages of SNMP-3-AUTHFAIL messages in your logs? In this article we will be dig into this issue and find out exactly what’s going and and why an SNMP-3-AUTHFAIL message might showing up in your logs …

As you probably know, access control lists (ACLs in further text) are a means of providing firewall protection. Except the basic division on standard and extended ACLs, we distinguish between time-based, reflexive ACLs, turbo ACLs, and many other. The focus of this article are time-based ACLs, when should you use …

Whether you are preparing for the Cisco IP Routing exam or you are an experienced network engineer planning to implement the Open Shortest Path First (OSPF) routing protocol, you should familiarize yourself with the capability to divide your network into separate OSPF areas. Using multiple OSPF areas reduces the frequency …

If you have ever experienced the ROMmon mode problem, you probably came across one of the following: configuration register forced the router to go to ROMmon mode during the boot process corrupt image (IOS) on Flash (indicated by bad_checksum message) router was unable to find the IOS (either on Flash …

Defining an access control list may seem a challenging and complex task, especially to those that have just delved into the world of computer networking and network security. The aim of this article is to explain the role of access control lists and basic concepts used to understand them. The …

VLANs are virtual LANs that is used to segregate broadcast domains in a layer 2 domain. Logically, VLANs allows you to setup multiple switches in a same physical switch. VLANs are used to isolate different types of traffic in IP networks like voice, data, management, web, and so on. Similarly, …

First Hop Redundancy Protocols (a.k.a. FHRP) are used to allow gateway redundancy. In this article, we cover the basics of this technology, with practical examples of configurations. I’m amazed at how the approach of the CCNA certification has changed since the time I took my test and entered the Cisco world …

Companies seek out VoIP because it enables productivity. Telecom assets were once defined by barriers – the kind that encumbered countless enterprise professionals. Even when, say, the phone and email needed to be used at the same time, these functions were siloed on separate hardware. Transcribing a voicemail to text …

Cisco CCNA Training:  IP Addressing Part 1 Here’s a great video to help you get a better understanding of ip addressing.

  Before I explain what and how explicit tracking of group membership works in IGMP, let me give you a brief introduction to IGMP. A brief introduction to IGMP: Internet Group Management Protocol ( IGMP ) is used by end hosts and routers to exchange multicast group membership information. IGMP …