Cisco Aironet 1231G and 1220B

I recently purchased a Cisco Aironet 1231G and a 1220B from eBay. The 1220B turned out to have been upgraded to a wireless G radio module. I have two Cisco access points that are G capable!

The 1231G was in Lightweight Access Point mode when I received it, and I followed Cisco's instructions to change it into an autonomous access point.

Configuring the APs isn't so straightforward if you've never worked with Cisco Aironet equipment. First you have to configure an SSID, then you have to attach the SSID to the radio module, and then you have to deal with encryption and authentication.

Authentication is specified in the SSID configuration, and the encryption is specified in the radio module configuration.

When everything was configured, I tried to search for the SSID, but it didn't appear. That was because I didn't put the SSID into guest-mode. By default, an SSID will not broadcast a beacon unless you add the guest-mode command. There can only be one guest SSID per BSSID.

The BSSID or Basic SSID is the mac address of the access point's radio. Recent IOS versions allow up to 8 concurrent BSSIDs and up to 16 regular SSIDs.

Here's where it gets really interesting: Neither the Ethernet interface nor the Dot11Radio interface were assigned IP addresses. They were both assigned to a bridge-group. A bridge-group is used to specify which interfaces will be participating in Cisco's IRB. Integrated Routing and Bridging is a way to connect two interfaces at the layer 2 level. This is how an access point connects the clients to the AP's wired network. It doesn't place the clients on a separate subnet because it is forwarding layer 2 traffic - not layer 3 traffic.

When a wireless client sends a packet to the access point, the way in which the AP forwards the packet  is very similar to how a switch forwards traffic. However there is a difference between how a switch works, and what the AP is doing.

When a switch receives a frame, it looks at the source mac address. If the address is not in the mac-address-table, the switch adds it to the table. The switch then looks at the frame's destination mac address. If it is in the mac-address-table, the switch forwards the frame out the interface listed in the entry. If it is not in the mac-address-table, the switch floods the frame out every interface in the vlan, except for the port on which the frame was received.

An access point by default will not have a mac-address-table. It does not do a lookup for every frame received. Instead, it forwards the frame from one interface to the only other interface.

There is a scenario in which the AP doesn't merely forward the frame to the next interface.
You can assign each bridge-group a virtual interface, much like the interfaces we use to telnet into a switch. It is called a BVI, or a Bridge Virtual Interface. The IP address is assigned to the BVI, and bridge routing must be turned on. By default, on IOS 12.3(8)JA, the BVI is already there, and the bridge routing is configured. It can only be configured to route for bridge-group 1. When I tried switching it, IOS gave me an error.

New Cisco 2621 Router!

Recently I purchased a Cisco 2621 router from eBay. It has two FastEthernet ports and came with a WIC1-DSU-T1. I removed the T1 card and installed it on my 2610 which I call R4.

I made some pretty big changes to my lab topology since the last few posts. I have been working on the CCNA material, and have changed my lab dozens of times. I will try to post a diagram of the current setup in a later post.

Passed the ICND1!

Today I passed the Interconnecting Cisco Network Devices 1 exam!
I am now a Cisco Certified Entry Networking Technician!

Studying for the CCENT/CCNA Together

I have not taken the ICND1 exam as of today although I am currently continuing my Cisco education by moving on to the ICND2 material.

I am using Wendell Odom's books:

CCENT/CCNA ICND1 Official Certification Guide as well as
CCNA ICND2 Official Certification Guide to learn the material.

I am using my lab extensively to practice everything from basic routing and switching to VLAN trunking and STP configuration.

Reading the second book has helped me with the ICND1 material a lot because it gave me a better understanding of many things the ICND1 just touches upon.

I plan on going the two-test route; First the ICND1 and then the ICND2.

The other method is to take the CCNA exam which includes all material from the ICND1 and ICND2.

Taking this route will allow me to be familiar with the testing centers and have a feel for the types of questions Cisco asks.

It will also split the CCNA material into two parts allowing me to study for each in more depth.

I have taken practice tests but I still have to study a little more.

Wish me luck!

My Cisco Lab With Addresses

Here is my lab layout with the interfaces and IP addresses included.

My Cisco Lab

This past Saturday, April 9th, I received my first complete Cisco lab via FedEx.

After negotiating with a very reputable seller, I ended up with a terrific beginner's lab for a terrific price!

My lab consists of:

Routers
• (1) Cisco 2610 Router with a WIC-1DSU-T1 and a WIC-1B-U
• (1) Cisco 2620 Router with a WIC-2T
• (2) Cisco 2620 Routers each with a WIC-1T

Switches

• (2) Cisco Catalyst 2950 Switches (24 FastEthernet ports)

Cables
• (2) Back-to-Back Smart-Serial cables (SS end is DCE)
• (1) Back-to-Back DB60 serial cable
• (4) Straight-Through RJ45 cables
• (3) DB9 Console cables
• (6) Power cables

Accessories
• (4) 2600 Rackmounts
• (2) 2900 Rackmounts

The Cisco 2610 Router was actually purchased from a different merchant. It has two WICs (Wan Interface Cards). The first is a T1 CSU/DSU card. The second is an ISDN BRI card. I don't have a use for either of these cards at the moment, but maybe one day I will.

The WIC-2T is a two port Smart-Serial card.
The WIC-1T is a one port DB60 serial card.

The lab is not mounted on a rack because I do not own a rack. With only six devices, it is not cost - and space - efficient to purchase a rack large enough to hold my devices with room for expansion.

This lab has been with me for a week, and it has helped me understand many networking concepts. If you do not own or have access to a real Cisco lab, spend the money and buy a lab.
You will be happy you did!

My Network

I received my routers and switches on Saturday night, but I will write about them in a later post.

I did however create a diagram of my current network using Microsoft's Visio, which I blogged about in an earlier post.

I left out the network addresses in order to maintain overall clarity. When I add the interfaces and their addresses I will post the updated diagram.

Microsoft Visio

I was looking on the internet for the software that everyone uses to create the Cisco lab diagrams. After reading through a few forums I was led to believe that the most popular software tool for this is Microsoft Visio.

Visio is a tool for creating diagrams of all types. Drawing network diagrams is one of Visio's many uses.

I visited the official Visio website in search of a free trial. After registering and logging in, I was left to choose between a 32-bit or a 64-bit version of Visio.

Because I have a 64-bit machine I chose the matching version. It took about twenty minutes to download Visio. I started the installer, and it gave me an error. Apparently my Microsoft Office Suite is 32-bit and even though my computer is 64-bit, Visio relies on the Office runtimes.

I need to download the 32-bit version of Visio. I haven't downloaded it yet, but I hope to download it and begin to familiarize myself with the software soon.

Expect some new diagrams in future posts!

My First Router

Last Friday I recieved the Cisco 2610 router I had ordered last Sunday. This is my first Cisco enterprise router. It has 1 built-in ethernet interface, a WIC-1B-U ISDN BRI card and a WIC-1DSU-T1 card. I am expecting three other routers very soon and I will write about them when they are delivered.

Cisco Certification

A little while ago I began studying for my Cisco certification. My first goal is to become a CCENT or Cisco Certified Entry Networking Technician. The exam I must take is the ICND1 640-822. Interconnecting Cisco Network Devices 1 is an exam to test your understanding of entry level networking theory and your ability to configure a small routed network. I hope to take the exam by the end of this year. Wish me luck!