Networks Articles

Computers » Networks | By Chris Bryant @ Monday, 8th May 2006 @ 2:06 PM

To pass the BCMSN exam and earn your CCNP, you've got to know HSRP inside and out! Part of that is knowing how the MAC address of the virtual router is derived, and another part is knowing how to change this address. We'll look at both features in this tutorial. We've got two routers on a segment running HSRP, so first we need to find out what the MAC address of the HSRP virtual router is. The show command for HSRP is show standby, and it's the first command you shou... more...

Computers » Networks | By Chris Bryant @ Monday, 8th May 2006 @ 2:04 PM

Part of studying for CCNA exam success is keeping all these new commands straight in your head! And let's face it, there are a lot of commands you need to know in order to pass the CCNA exam and earn that certification. Here's a review of some very important distance vector and static routing commands you need to know, along with their proper usage and console output. Bandwidth IGRP makes a default assumption that any Serial interface running IGRP is connected to a T1 line, ... more...

Computers » Networks | By Chris Bryant @ Monday, 8th May 2006 @ 1:57 PM

When you're studying for the BSCI exam on the way to earning your CCNP certification, it's safe to say that BGP is like nothing you’ve studied to this point. BGP is an external routing protocol used primarily by Internet Service Providers (ISPs). Unless you work for an ISP today or in the future, you may have little or no prior exposure to BGP. Understanding BGP is a great addition to your skill set – and you have to know the basics well to pass the BSCI exam. Note that I said... more...

Computers » Networks | By Chris Bryant @ Thursday, 4th May 2006 @ 7:57 AM

To pass the BSCI exam and earn your CCNP, you've got to keep a lot of details in mind. It's easy to overlook the "simpler" protocols and services such as static routing and distance vector protocols. With this in mind, here's a quick review of some details you should know for success in the exam room and real-world networks! When packets need to be routed, the routing table is parsed for the longest prefix match if multiple paths exist with the same prefix length, t... more...

Computers » Networks | By Chris Bryant @ Thursday, 4th May 2006 @ 7:57 AM

Not only is your CCNA exam going to have questions on VLAN trunking protocol, almost any network that has more than one VLAN is going to have VTP running. Whether you're planning on passing the CCNA exam or just brushing up on your networking skills, this VTP tutorial will help you learn the basics of this important protocol. VTP allows switches to advertise VLAN information between other members of the same VTP domain. VTP allows a consistent view of the switched network across a... more...

Computers » Networks | By Chris Bryant @ Thursday, 4th May 2006 @ 7:56 AM

Not only is your CCNA exam going to have questions on VLAN trunking protocol, almost any network that has more than one VLAN is going to have VTP running. Whether you're planning on passing the CCNA exam or just brushing up on your networking skills, this VTP tutorial will help you learn the basics of this important protocol. VTP allows switches to advertise VLAN information between other members of the same VTP domain. VTP allows a consistent view of the switched network across a... more...

Computers » Networks | By Chris Bryant @ Thursday, 4th May 2006 @ 7:55 AM

To pass the BCMSN exam and earn your CCNP certification, you've got to know HSRP inside and out. While the operation and basic commands of HSRP are pretty simple, there are some important details that are easily overlooked but are vital in getting HSRP to work the way you want it to. Let's take a look at using the priority command correctly on both the exam and in production networks. A key value in the show standby command is the priority. The default is 100, and the router w... more...

Computers » Networks | By Chris Bryant @ Monday, 1st May 2006 @ 9:57 AM

To pass the CCNA exam and earn this important certification, you’ve got to know switching inside and out. While you’re learning all the basic switching theory, make sure to spend some time with the one of three switching modes Cisco routers can use. Store-and-Forward is exactly what it sounds like. The entire frame will be stored before it is forwarded. This mode allows for the greatest amount of error checking, since a CRC (Cyclical Redundancy Check) is run against the frame before it... more...

Computers » Networks | By Chris Bryant @ Monday, 1st May 2006 @ 9:56 AM

To earn your CCNP certification and pass the BCMSN exam, you've got to know what HSRP does and the many configurable options. While the operation of HSRP is quite simple (and covered in a previous tutorial), you also need to know how HSRP arrives at the MAC address for the virtual router - as well as how to configure a new MAC for this virtual router. This puts us in the unusual position of creating a physical address for a router that doesn't exist! The output of show standby... more...

Computers » Networks | By Chris Bryant @ Monday, 1st May 2006 @ 9:55 AM

CCNP exam success, particularly on the BSCI exam, demands you understand the details of route summarization. This skill not only requires that you have a comfort level with binary conversions, but you have to know how and where to apply route summarization with each individual protocol. You also have to know the "side effects" of route summarization. With OSPF, there will actually be an extra interface created at the point of summarization, and this catches a lot of CCNP candida... more...

Computers » Networks | By Chris Bryant @ Saturday, 29th April 2006 @ 9:56 AM

Defined in RFC 2281, HSRP is a Cisco-proprietary protocol in which routers are put into an HSRP router group. Along with dynamic routing protocols and STP, HSRP is considered a high-availability network service, since all three have an almost immediate cutover to a secondary path when the primary path is unavailable. One of the routers will be selected as the primary ("Active", in HSRP terminology), and that primary will handle the routing while the other routers are in standby, r... more...

Computers » Networks | By Chris Bryant @ Saturday, 29th April 2006 @ 9:55 AM

Passing the BSCI exam and earning your CCNP is all about knowing the details, and when it comes to EIGRP SIA routes, there are plenty of details to know. A quick check in a search engine for "troubleshoot SIA" will bring up quite a few matches. Troubleshooting SIA routes is very challengin in that there's no one reason they occur. View the EIGRP topology table with the show ip eigrp topology command, and you'll see a code next to every successor and feasible successor. A... more...

Computers » Networks | By Chris Bryant @ Tuesday, 25th April 2006 @ 9:03 AM

The most common method of configuring ISDN is with dialer maps, but dial information can also be configured on a logical interface. To pass the CCNA exam, you must know how to configure and troubleshoot both dialer maps and dialer profiles. Dialer Profiles allow different dialing information to be configured onto logical interfaces. The logical interfaces may have different dialing destinations, different remote router names, etc., but they’ll be using the same physical interface.<... more...

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 considered Qo... 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 poli... 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 signif... 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 hun... 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 groups -... 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 tran... more...