Cisco 877W - Integrated Services Router User Manual download pdf (Page 9)

Q&A

Q. At what frequency do the integrated access points communicate?

A. Based on 802.11b/g specifications, in the United States, the integrated access points use channels 1-11. In

Europe, the Middle East, and Asia, they use channels 1-14. For more information, visit

http://cisco.com/en/US/products/ps5853/products_configuration_guide_chapter09186a008067e8e9.html.

Q. What is a WEP key? What are the security issues associated with WEP and how are they overcome?

A. WEP is the encryption algorithm built into the 802.11 (Wi-Fi) standard. WEP encryption uses the RC4 Stream

Cipher with 40- or 104-bit keys and a 24-bit initialization vector.

The security issues with WEP are as follows:

●

There is a great deal of administrative overhead maintaining a shared WEP key.

●

WEP has the same problem as all systems based on shared keys. Any secret given to one person becomes

public after a period of time.

●

The initialization vector that seeds the WEP algorithm is sent in clear text.

●

The WEP checksum is linear and predictable.

The collection of enhancements added to WEP to address the above-listed issues is called Temporal Key

Integrity Protocol (TKIP).

Like WEP, TKIP uses Ron's Code 4 (RC4) encryption. However, TKIP enhances WEP by adding measures

such as per packet key hashing, Message Integrity Check (MIC), and broadcast key rotation to address known

vulnerabilities of WEP.TKIP uses RC4 stream cipher with 128-bit keys for encryption and 64-bit keys for

authentication.

Q. How can you recover forgotten passwords?

A. To recover forgotten WEP passwords you must go into the access point portion of the router using the Cisco

IOS Software CLI or the Cisco SDM graphical interface and change the WEP password.

Q. How many clients can associate to the unit?

A. It is recommended that each router associate only as many clients as each router will support in the number of

simultaneous users. With Cisco 870 Series routers, the recommendation is up to 20 clients; with the Cisco 850

Series, the recommendation is up to 10 clients.

Q. What is the typical range for an access point?

A. The 802.11b basic range is 50 to 100 feet, and there is a 300-foot maximum. Within a typical office

environment, most access points can provide good wireless coverage up to 150 feet. The 802.11b standard

uses the same radio signaling frequency-2.4 GHz-as the original 802.11 standard. Being an unregulated

frequency, 802.11b gear can incur interference from microwave ovens, cordless phones, and other appliances

using the same 2.4 GHz range. However, by installing 802.11b gear a reasonable distance from other

appliances, interference can easily be avoided.

The 802.11g standard attempts to combine the best of 802.11a and 802.11g. The 802.11g standard supports

bandwidth up to 54 Mbps, and it uses the 2.4 GHz frequency for greater range. The 802.11g standard is

backward compatible with 802.11b, meaning that 802.11g access points will work with 802.11b wireless network

adapters and vice versa.

Q. Are Cisco 800 Series Integrated Services Routers and their integrated access points interoperable with

the Cisco Aironet 340, 350, 1100, and 1200 Series products?

A. Yes. The Cisco 800 Series Integrated Services Routers are interoperable with the other Cisco wireless products

and Wi-Fi certified products. The routers will always work in Root AP mode and do not support Wireless Uplink

to another AP.

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Q&A 1
Table 4. Annex-M Masks 7

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Cisco 877W - Integrated Services Router User Manual Page 9

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