CompTIA A_ Certification All-In-One Exam Guide, Seventh Edition - Michael Meyers [426]
Figure 24-7 Wireless configuration utility
Ad hoc Mode
Ad hoc mode is sometimes called peer-to-peer mode, with each wireless node in direct contact with every other node in a decentralized free-for-all, as shown in Figure 24-8. Two or more wireless nodes communicating in ad hoc mode form what’s called an Independent
Figure 24-8 Wireless ad hoc mode network
Basic Service Set (IBSS). Ad hoc mode networks are suited for small groups of computers (less than a dozen or so) that need to transfer files or share printers. Ad hoc networks are also good for temporary networks such as study groups or business meetings.
Infrastructure Mode
Wireless networks running in infrastructure mode use one or more WAPs to connect the wireless network nodes to a wired network segment, as shown in Figure 24-9. A single WAP servicing a given area is called a Basic Service Set (BSS). This service area can be extended by adding more WAPs. This is called, appropriately, an Extended Basic Service Set (EBSS).
Figure 24-9 Wireless infrastructure mode network
Wireless networks running in infrastructure mode require more planning and are more complicated to configure than ad hoc mode networks, but they also give you finer control over how the network operates. Infrastructure mode is better suited to networks that need to share dedicated resources such as Internet connections and centralized databases.
Wireless Networking Security
One of the major complaints against wireless networking is that it offers weak security. In many cases, all you need to do to access a wireless network is walk into a WAP’s coverage area, turn on your wireless device, and connect! Furthermore, data packets are floating through the air instead of safely wrapped up inside network cabling. What’s to stop an unscrupulous PC tech with the right equipment from grabbing those packets out of the air and reading that data himself?
Wireless networks use three methods to secure access to the network itself and secure the data that’s being transferred. The service set identifier (SSID) parameter—also called the network name—is used to define the wireless network. This is very handy when you have a number of wireless networks in the same area.
SSID
One of the main security weaknesses with wireless networks is that, out of the box, no security is configured at all. Wireless devices want to be heard, and WAPs are usually configured to broadcast their presence to their maximum range and welcome all other wireless devices that respond.
Always change the default SSID to something unique, and change the password right away. Configuring a unique SSID name and password is the very least that you should do to secure a wireless network. The default SSID names and passwords are well-known and widely available online. This is intended to make setting up a wireless network as easy as possible but can cause problems in places with a lot of overlapping wireless networks. Each wireless network node and access point needs to be configured with the same unique SSID name. This SSID name is then included in the header of every data packet broadcast in the wireless network’s coverage area. Data packets that lack the correct SSID name in the header are rejected.
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EXAM TIP Changing the default SSID for the WAP is the first step in setting up a new wireless network.
Another trick often seen in wireless networks is to tell the wireless device not to broadcast the SSID. People not authorized to access the network will have a harder time knowing it’s there.
MAC Address Filtering
Most WAPs also support MAC address filtering, a method that enables you to limit access to your wireless network based on the physical, hard-wired address of the units’ wireless NIC. MAC address filtering is a handy way of creating a type of “accepted users” list to limit access to your wireless network, but it works best when you have a small number