The Transcender Team Weblog

Troy’s checklist for preparing for the CCNA: Objective 8

Thanks for returning for the final installment of my review checklist for the CCNA exam. In this session we will cover the topics included in Objective 8: Implement and Verify WAN links.  Let’s get started!

You should be able to describe the differences between the categories of data transfer between physical locations. These include:

• Cell switching – Cell switching is a WAN switching technology that is used by ATM. ATM is an International Telecommunication Union-Telecommunications (ITU-T) standard for the transmission of data, voice, or video traffic. It uses a fixed size frame of 53 bytes, known as cells. Out of these 53 bytes, the initial five bytes are header information and the rest of the 48 bytes are the payload.
• Packet switching – Packet switching is popularly used for data transfer, as data is not delay-sensitive like voice traffic is, and it does not require real-time transfer from a sender to a receiver. With packet switching, the data is broken into labeled packets and transmitted using packet-switching networks.
• Circuit switching – Circuit switching dynamically establishes a virtual connection between a source and destination. The virtual connection cannot be used by other callers unless the circuit is released. Circuit switching is the most common method used by the Public Switched Telephone Network (PSTN) to make phone calls. A dedicated circuit is temporarily established for the duration of call between caller and receiver. Once the caller or receiver hangs up the phone, the circuit is released and is available for other users.

You should how to configure a serial link for a WAN connection. Make sure that you know how to use these commands: Continue Reading Troy’s checklist for preparing for the CCNA: Objective 8…

Troy’s checklist for preparing for the CCNA: Objective 6

This week we cover Objective 6 of 640-802, Identify Security threats to a network and describe general methods to mitigate those threats. This objective, while a small part of the exam, is very important in the real world. First you should be familiar with all types of attacks that a network can experience, and second, you should know the security features or approaches that can mitigate theses attacks.

The above answers are general in nature. You also should know the specific Cisco feature that can be used to mitigate these attacks, such as: Continue Reading Troy’s checklist for preparing for the CCNA: Objective 6…

Troy’s checklist for preparing for the CCNA: Objective 5

Hello, intrepid CCNA seekers. I salute your persistence if you’ve stuck with me this far! This week we venture into the wild and woolly world of wireless. Specifically we cover the following: Objective 5 of 640-802, Explain and select the appropriate administrative tasks required for a WLAN. It’s a short and sweet objective, especially compared with the whopper that was Objective 4.

(Here’s the previous coverage of Objective 1, Objective 2, Objective 3, Objective 4 Part 1, and Objective 4 Part II. The full list of CCNA objectives is at https://cisco.hosted.jivesoftware.com/community/certifications/ccna/ccna_exam?view=overview.)

First you should know all of the major standard creating and regulatory bodies that influence 802.11 (WLAN) networking:

• Wi-Fi Alliance (no, they have nothing to do with your old record player, that’s Hi-Fi) – The Wireless Fidelity (Wi-Fi) Alliance is an organization formed to provide interoperability between different WLAN vendors.
• IEEE – the Institute of Electrical and Electronics Engineers (IEEE) is a non-profit worldwide organization that creates standards for various industries, including information technology (IT) and telecommunications.  802.11 wireless networking standards are defined by the IEEE.
• FCC – the Federal Communications Commission (FCC) is a U.S. government agency that regulates communication standards in the areas of wire, television, cable, and satellite communications. It also regulates the use of radio frequencies (RF) and power of transmitters.

Know all of the following terms and how the components make up a wireless network:

• Ad Hoc network
• Infrastructure network
• ESS, BSS, IBSS
• SSID

Also, know how to create an ESS. (If you put the same SSID on each access point, they will all be in the same ESS while each maintains its own BSS.) If you need some background, here’s a good basic article from Cisco Press: Wireless LANs: Extending the Reach of a LAN

Before I continue, here’s a joke.

Q. What are the three most important things to understand about wireless networking?

A. Security, security, security, security, and security.

Seriously, folks, there is a lot of wireless security to know. If you only have room in your memory for a few key facts, then here’s where to focus. It might help to generate a timeline of each security technology and make a note of 1. what it features, 2. what it replaced or supplemented, and 3. where it’s currently implemented, if at all.

• Know the common wireless standards: 802.11, 802.11g, and 802.11b.
• Be familiar with the components of WEP, WPA, and WPA-2, including the differences between these technologies.
• WPA-2 operates in two modes: Enterprise and Personal. Know what encryption is used in each mode. In Enterprise it uses AES/CCMP. In Personal it uses a shared key.
• WPA (the older, less powerful technology) uses MIC/TKIP for encryption.
• WEP  uses static shared secrets and is the weakest security listed here.
• IEEE 802.11i is an amendment to the 802.11 standard that is meant to address the weaknesses of WEP. WPA2 is an implementation of 802.11i.
• LEAP is a form of EAP that uses passwords and a RADIUS server. It can also dynamically change the WEP keys, if you are also using WEP.
• Be familiar with security concepts like MAC address filters, port-based access control, and wireless intrusion detection and prevention.
• Understand what is meant by wireless security terms like sniffing and war driving.

That’s pretty much it! Objective 5 is not a major part of the exam, so you can focus your study on these topics for good coverage.

Troy’s checklist for preparing for the CCNA: Objective 4 – part 2

Welcome to Part 2 of Objective 4: Configure, verify, and troubleshoot basic router operation and routing on Cisco routers. Don’t forget Objective 4 – Part 1.

Be able to compare and contrast the capabilities and idiosyncrasies of common routing protocols, especially:

•    RIPv1 and RIPv2
•    OSPF
•    EIGRP

You should know details like:

•    The metrics and routing algorithm that each protocol uses
•    Which protocols are classless and which are classful
•    How to enable each protocol globally and then how to enable each protocol on an interface
•    Each protocol’s default administrative distance

For example, how does OSPF select the designated router on a segment? On a related note, what determines the OSPF router ID? Can you interpret the show ip ospf neighbor command output?

Quick tutorial. Here’s how to enable OSPF and assign the router to an area:

Router(config)#router ospf 1
Router(config-router)#network 192.168.5.0 0.0.0.255 area 0 (yes, you use wildcard mask here)

Here’s how to enable EIGRP globally and enable it on an interface:

router(config) # router eigrp [autonomous-system]
router (config-router) # network x.x.x.x
router (config-router) # network y.y.y.y

Know how to set up a hyperterminal connection to a router or a switch, and the required settings for the serial connection it uses. Hint: Continue Reading Troy’s checklist for preparing for the CCNA: Objective 4 – part 2…

Troy’s checklist for preparing for the CCNA: Objective 4 – part 1

Welcome to to this week’s exciting double feature. Today we’ll dive into what you need to know in Objective 4: Configure, verify, and troubleshoot basic router operation and routing on Cisco routers. There’s so much material here that I’ve broken it up into two posts. Get off the Internet and let’s get started!

(Here’s the previous coverage of Objective 1, Objective 2 and Objective 3. The full list of CCNA objectives is at https://cisco.hosted.jivesoftware.com/community/certifications/ccna/ccna_exam?view=overview.)

For Objective 4, you need to know how routers handle and alter the packets they receive. Specifically, you should understand which addresses in the packet are changed by the router (MAC addresses), and which remain the same in the routing process (source and destination IP addresses).

You should be able to read a routing table and pull information out, such as:

• The meaning of the codes next to each entry (C, R, S, I, etc). These codes indicate the method by which the route was learned. When you run the command on a router, there is a legend (a key) at the beginning that explains the codes, but that legend may be truncated from the output shown on the exam (those sneaky rascals!)
• The meaning of all that stuff in brackets next to each route, i.e. [160/5]. Answer: the left side of the slash is the administrative distance (AD) and the right side is the route metric.

For a more in-depth review, study the Cisco command reference for show ip route and related commands.

You should know what a default route is and how to configure one. You also know when it is appropriate to use them (on edge routers or routers with only one connection to the rest of the network, and thus only one route to anything). You should also know that a default route’s main benefit is to reduce the number of routes in the routing table.

You should be familiar with the concept of route redistribution, its purpose, and how it is configured. You should also know how to alter the default behavior of route redistribution by using distribution lists. Make sure that you understand to use an access list to control the redistribution, but apply the list as a distribute list under the configuration of the routing protocol as shown below (taken from show run). In this example, we have instructed the router to only redistribute the network 0.0.0.0 and 10.108.0.0. and deny everything else:

access-list 10 permit 0.0.0.0
access-list 10 permit 10.108.0.0
access-list 10 deny 0.0.0.0 255.255.255.255
router eigrp 1
network 10.108.0.0
distribute-list 10 in

You should understand basic operation of the internals of the router. Specifically, you should know what the following terms and concepts mean, how they all work together, and what is stored in each location:

• Running configuration
• Startup configuration
• NVRAM
• FLASH
• ROM

You should be familiar with possible ports you might find on a router (Serial, BRI, FastEthernet, etc.), and what type of cable is required to connect various devices (straight-through, crossover, rollover/console). (This is also covered in Objective 2.)

Understand how the following mechanisms work:

• Split horizon
• Poison reverse
• Triggered updates
• Count to infinity
• Gateway of last resort

Know how to configure a router from start to finish. This topic is an excellent one to practice in real life. If you don’t have the gear to practice with, get a lab simulator – I personally recommend the Kaplan IT CCNA simulator.

Here are some good examples of basic router configurations:

• Set a Telnet password
• Set an encrypted password
• Configure an IP address on an interface and enable the interface
• Enable a routing protocol on an interface

Very Important: Know your command prompts and the commands for getting in and out of the various prompt levels. Know what commands and functions can be performed at the various prompts. Always check the command AND the prompt in output. Careless errors can cost you.

Practice, practice, practice!!!  You will not have time to figure out how to do these operations on the exam; you only have time to do them. On the exam you will have about 1 to 2 minutes per question. That goes quick if you don’t quite know what you’re doing.

~~Continued in Part 2~~