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Cisco Dial Peers, Part 1

Article | Nov. 24, 2009

Cisco Unified Communication H.323 and SIP gateways will require a dial plan on those gateways to extend calls to endpoints that may be configured. An endpoint may be either an analog or digital voice port that would provide connections to the public switch telephone...

“nat-control” versus “no nat-control”

Article | Nov. 24, 2009

ASA and PIX software version 7.0 introduced the configuration command nat-control which didn’t exist in previous versions of code. Although training course material for both the SNAF (Securing Networks with ASA Fundamentals) and SNAA (Securing Networks with ASA Advan...

Cisco IP Phone Audio Codecs

Article | Nov. 23, 2009

Cisco IP phones support a variety of different audio codecs. In this post, I will explain some of the differences and explain which versions of CUCM and the Cisco IP phones support the various audio codecs. Audio codecs are responsible for sampling human speech (a s...

QoS Part 4 – QoS Mechanisms

Article | Nov. 12, 2009

In the previous discussion on QoS, the uses of Per-Hop Behaviors DiffServ to mark packets were identified and discussed in detail. Today’s post will identify the mechanisms to implement QoS. The five main categories of tools used to implement QoS are as follows. Cl...

Quality of Service, Part 3

Article | Nov. 04, 2009

In the previous discussion on QoS the Per-Hop Behaviors DiffServ uses to mark packets were identified. These where listed as:Expedited Forwarding (EF) – RFC 3246 – Provides a strict priority serviceAssured Forwarding (AF) – RFC 2597 – Provides a qualified delivery gu...

What’s an RFC and what can they do for me?

Article | Sep. 16, 2009

No matter what book or manual you use to study for the CCNA examination, you will see various protocols and processes referencing an RFC. And, although frequently referenced, the RFCs are seldom actually included in the documentation. So, the logical question becomes...

CUCM Call Throttling

Article | Sep. 08, 2009

Cisco Unified Communications Manager (CUCM) includes a feature called "call throttling" that denies new call attempts when the system is in a state that may lead to delayed dial tone. The Real Time Monitoring Tool (RTMT) will generate a code yellow alert when call t...

Address Resolution Protocol (ARP)

Article | Aug. 28, 2009

When sending data end-to-end through a network, routers are used in internetworking to create a virtual network from one device to another, either locally or globally. Routers are configured to operate with most common network protocols. That means they know the form...

Network Layer Utilities: End-to-End Data Delivery

Article | Aug. 22, 2009

Find out which OSI layer is concerned with reliable end-to-end delivery of data - and more. Get answers to your OSI reference model and network layer questions here.

Call Admission Control

Article | Aug. 20, 2009

Call Admission Control (CAC) is often times included as part of the same topic as Quality of Service (QoS), when in actuality CAC is a separate and complete topic itself. QoS is defined as traffic engineering on a packet switched network. This definition means movin...

Exchange 2010 Transport Fundamentals

Article | Aug. 17, 2009

Exchange 2010 builds upon the significant changes to the transport that were made in Exchange 2007. In this article, I'll review the transport pipeline and routing components and list some of the new architectural and administrative enhancements to the Exchange 2010...

RFC 2833 and DTMF Relay

Article | Aug. 12, 2009

Devices must send dual-tone-multi-frequency (DTMF) when a phone call is routed to an automated system. Automated attendant (AA), voicemail (VM), or interactive voice response (IVR) systems are some examples of the types of automated systems that can pick up phone calls.

Understanding RIP v2

Article | Aug. 05, 2009

So far, in our discussion of Router Information Protocol (RIP), we’ve discussed the basics and also verified and reviewed RIP version1. We stated that RIP version 1 is a classful routing protocol that used FLSM and sent it routing updates without the subnet mask.  In...

Basics of Understanding RIP

Article | July 30, 2009

RIP is a protocol that is used for routing IP networks. It was designed in the early 1980’s for communication between gateways (computers with two NIC’s). It is the oldest routing protocol used by the network industry and is considered by many to be inefficient or bo...

FTP vs. TFTP

Article | July 15, 2009

Recently we've been comparing using Telnet with Secure Shell protocol to allow remote access to a device such as a router or switch. Now, we're going to compare File Transfer Protocol (FTP) and Trivial File Transfer protocol (TFTP) for a Cisco router or switch. These...

Static Routing

Article | July 14, 2009

You may have noticed that it’s the dynamic routing protocols that get all the glory. Since I like rooting (routing?) for the underdog, let’s talk about static routes! As you may recall, a router has three methods for learning a route. A route can appear in the routi...

Calculating VoIP Bandwidth

Article | July 08, 2009

When integrating a Voice over IP (VoIP) system into an existing network it is very important to have a good understanding of how much bandwidth is utilized for each call on the network. For most people, just starting out the bandwidth calculations can be a very daunt...

E.164 – The modern dial plan

Article | July 02, 2009

When we are addressing Voice over IP we need to remember that essentially we would like to reach customers over the PSTN or SS7 network. The only avenue to date to do this, is by using something called the telephone number. However, that number has undergone some cha...

Access Control Lists (ACLs) – Part 6

Article | June 23, 2009

As you may recall, we can use extended IP ACLs to filter packets based on source address, destination address, transport layer protocols, and other options, as follows: access-list 106 permit tcp host 1.2.3.4 host 5.6.7.8 eq telnet For a packet to be permitted by...

Access Control Lists (ACLs) – Part 5

Article | June 19, 2009

Having discussed general ACL rules and syntax, let’s now turn to the differences between standard and extended ACLs. As you might recall, numbered ACLs fall into several ranges: 1 – 99: Standard IP 100 – 199: Extended IP 1300 - 1999: Standard IP (expanded rang...

Printing PowerPoint Slides with Notes

Article | June 11, 2009

If you create presentations using the notes feature in PowerPoint, you probably have found yourself wanting to print multiple slides on one page (handouts) with the notes associated with those slides displayed on the same page. This layout can often help you better p...

Telnet vs SSH

Article | June 10, 2009

In our last blog series we discussed multiple access commands that can be configured on a router or a switch. These commands included cosmetic commands such as logging synchronous and exec-timeout that can be configured on the console port. We also discussed configur...

Telepresence Bandwidth Requirements

Article | June 08, 2009

Telepresence is a set of technologies that allow video conferencing in such a way that the user feels as if they are actually at the remote site. Cisco sells a variety of platforms in the telepresence space supporting up to three 65” high definition video displays,...

Configuring Terminal Access Banners

Article | June 04, 2009

In my last post we discussed basic terminal access. The commands that I reviewed were for accessing the console port or vty lines of a Cisco router or switch. Network administrators should configure banners for legal and liability purposes. Now, we will see how to co...

Basic Cisco Terminal Access

Article | June 02, 2009

Cisco Switches and Routers running the Internet Operating System (IOS) have many things in common. Configuring these devices of course, is a skill that is sharpened the more you touch the device. During this post, our discussion will primarily focus on the basic comm...

Triple Constraints Model

Article | June 01, 2009

The triple constraints model has been one of the main staples for teaching project management for as long as I can remember. The model is generally represented by a triangle with Scope on the horizontal leg, Time on the left leg, Cost or Resources on the right leg an...

Access Control Lists (ACLs) – Part 2

Article | May 29, 2009

In ACLs - Part 1 we learned the basics of access lists, including the facts that ACLs: Are created in global config mode End with an implicit “deny any” (which can be overridden) Must be placed into service somewhere to have any effect Thus, the commands: Rout...

Routing Tables - Part 2

Article | May 22, 2009

In Routing Tables part one, we covered the basic purpose of a routing table and how an end device or intermediate device such as a router or multilayer switch can route based off its table. We also viewed different routing tables and how they are used to find a given...

Eleven Myths About 802.11 Wi-Fi Networks

Webinar – Recorded | Oct. 06, 2006

Wi-Fi networks have been misunderstood by much of the IT community since their inception. Even the reasons for this misunderstanding are kind of hard to understand. The result has been that myths about 802.11 (better known as Wi-Fi) networks have grown almost as fast as the technology itself. In this web seminar, we'll examine 11 common Wi-Fi myths and explore ways to use correct information to make your networks scalable, secure and satisfying for your users.