Networks Articles

Computers » Networks | By Chris Bryant @ Tuesday, 25th April 2006 @ 8:57 AM

To pass the CCNP exams, you’ve got to master Quality of Service, and the first step in doing so is knowing the differences between the different QoS types. Now this being Cisco, we can\'t just have one kind of QoS! We\'ve got best-effort delivery, Integrated Services, and Differentiated Services. Let\'s take a quick look at all three. Best-effort is just what it sounds like - routers and switches making their \"best effort\" to deliver data. This is consider... more...

Computers » Networks | By Chris Bryant @ Monday, 24th April 2006 @ 9:55 AM

To pass the BSCI exam, you need to know the difference between IRDP and HSRP. While they have the same basic function, the operation and configuration of each are totally different. The aim of both is to allow hosts to quickly discover a standby router when the primary router fails. IRDP is commonly used by Windows DHCP clients and several Unix variations, but you do see it in Cisco routers as well. IRDP is defined in RFC 1256. IRDP routers will multicast Hello messages that host d... more...

Computers » Networks | By Chris Bryant @ Monday, 24th April 2006 @ 9:55 AM

QoS - Quality of Service - is a huge topic on both the BCMSN exam and real-world networks. QoS is so big today that Cisco\'s created separate specialist certifications that cover nothing but QoS! It can be an overwhelming topic at first, but master the fundamentals and you\'re on your way to exam and job success. If you work with QoS at any level - and sooner or later, you will - you\'ve got to know how to write and apply QoS policies. Creating and applying such a p... more...

Computers » Networks | By Chris Bryant @ Monday, 24th April 2006 @ 8:55 AM

Passing the CCNA is tough, and one of the toughest parts is keeping all the acronyms straight! Frame Relay has plenty of those, and today we\'re going to examine what DLCIs do and how they\'re mapped on a Cisco router. Frame Relay VCs use Data-Link Connection Identifiers (DLCI - pronounced \"del-see\") as their addresses. Unlike other Cisco technologies, VCs have only a single DLCI in their header. They do not have a source and destination. DLCIs have local si... more...

Computers » Networks | By Chris Bryant @ Thursday, 20th April 2006 @ 10:42 AM

To be truly prepared for your CCNA and CCNP exams, you need real hands-on experience with real Cisco routers and switches. However, a production network is a really bad place to practice your configurations, but an excellent way to get fired and/or sued. The key to becoming a true CCNA and CCNP is assembling your own Cisco home lab. You don\'t have to spend a lot of money to do so; used Cisco equipment is cheaper than ever. It\'s robust as well - I\'ve bought literally ... more...

Computers » Networks | By Chris Bryant @ Thursday, 20th April 2006 @ 9:24 AM

QoS is a big topic on your BCMSN and CCNP exams, and for good reason. As more and more traffic flows through today\'s networks, accurately applying QoS to both your routers and switches becomes more important. Note the phrase \"accurately applying\". You must have a plan in place before you start configuring QoS on your switches, and to create such a plan you should use Cisco\'s Three-layer Hierarchical Model. This model breaks switches down into three main grou... more...

Computers » Networks | By Chris Bryant @ Thursday, 20th April 2006 @ 9:18 AM

While routers accept and generate broadcasts, they do not forward them. This can be quite a problem when a broadcast needs to get to a device such as a DHCP or TFTP server that\'s on one side of a router with other subnets on the other side. If a PC attempts to locate a DNS server with a broadcast, the broadcast will be stopped by the router and will never get to the DNS server. By configuring the ip helper-address command on the router, UDP broadcasts such as this will be tra... more...

Computers » Networks | By Chris Bryant @ Tuesday, 18th April 2006 @ 12:07 PM

I know from experience that part of the excitement and anxiety of putting together your own CCNA / CCNP home lab is deciding what to buy! While you can make a workable home lab out of almost any combination of Cisco routers and switches, some routers are better suited for home lab work than others because they can fill multiple roles. When you buy CCNA or CCNP \"lab kits\" - bundles of routers and switches - you can get a little confused about whether you\'re getting a good d... more...

Computers » Networks | By Chris Bryant @ Tuesday, 18th April 2006 @ 12:03 PM

If a Layer Two switch doesn\'t have the capabilities to run IGMP Snooping, it will be able to run CGMP - Cisco Group Membership Protocol. CGMP allows the multicast router to work with the Layer Two switch to eliminate unnecessary multicast forwarding. CGMP will be enabled on both the multicast router and the switch, but the router\'s going to do all the work. The router will be sending Join and Leave messages to the switch as needed. PIM must be running on the router interf... more...

Computers » Networks | By Chris Bryant @ Monday, 17th April 2006 @ 8:57 AM

Multicasting is a vital topic on your BCMSN, CCNP, and CCIE exams, and it can also be very confusing when you first start studying it. Multicasting uses concepts that are unlike anything you\'ve run into in your routing protocol studies, and that can throw you at first. I speak from experience that multicasting is like any other Cisco technology - learn the basics, master the fundamentals, and then build your skills on that foundation. One such fundamental is the RPF Check, or R... more...