Table Of Contents
Release Notes for Cisco Aironet Workgroup Bridges Running Firmware Release 8.80
May 31, 2002
These release notes describe features and caveats contained in this maintenance release for Cisco Aironet Workgroup Bridges running firmware release 8.80. These release notes also contain important information about the device.
These release notes describe the following topics:
Workgroup bridges are small, standalone units that provide wireless infrastructure connections for Ethernet-enabled devices. A device connected to a bridge communicates with a network infrastructure through Cisco Aironet Access Points.
The workgroup bridge connects to a hub through a standard Ethernet port using a 10BaseT/RJ-45 (twisted pair) connector, and up to eight client devices can be connected to the hub. You can use an Internet browser or Telnet to configure the workgroup bridge.
You must have a Cisco Aironet 340 or 350 Series Workgroup Bridge to install firmware version 8.80.
Minimum Firmware Version Required on Access Points
Access points with which the workgroup bridge associates must contain firmware version 11.05 or later. The firmware version number appears in the upper-left corner of most access point management screens in the browser interface and at the top of the home (Summary Status) page in the command-line interface.
Upgrading to a New Firmware Release
Determining the Firmware Version
The firmware version number appears in the top left corner of the screen in the browser-based management system. To view the browser-based management system, type the device's IP address in the Internet browser address line.
Follow these steps to upgrade the firmware in your workgroup bridge:
Step 1 Use one of the following URLs to find firmware version 8.80
Step 2 Make sure you select the firmware version 8.80 for 340 and 350 series workgroup bridges.
Step 3 In the Filename column, click [firmware version 8.80 for workgroup bridges]. Follow the instructions for saving the file to your local drive.
Step 4 Use an Internet browser to open the management system on the workgroup bridge. To browse to the management system, type the workgroup bridge's IP address in the browser address line and press Enter.
Step 5 When the management system opens, click Allow Config Changes in the top left corner of the page.
Step 6 Click Load in the Diagnostics column near the top of the page.
Step 7 In the Value column, click Browse. Find the local drive where you saved the new firmware version and select the firmware file.
Step 8 Click Send. The new firmware is loaded and the workgroup bridge reboots.
This section describes new features in firmware version 8.80.
Key Hashing Support
Firmware version 8.8 supports key hashing. When a WEP key is used to encrypt and decrypt transmitted data, each packet includes an initialization vector (IV), a 24-bit field that changes with each packet. The RC4 Key Scheduling Algorithm creates the IV from the base WEP key. A flaw in the WEP implementation of RC4 allows the creation of "weak" IVs that give insight into the base key. A hacker can exploit this flaw by gathering packets encrypted with the same key and using the weak IVs to calculate the base key.
By hashing the base key with the IV to create a new key for each packet, WEP key hashing removes the predictability that an intruder relies on to determine the WEP key by exploiting the IVs. Key hashing is implemented in the radio firmware on both the transmitter and recipient of encrypted packets.
Message Integrity Check Support
Firmware version 8.80 supports message integrity check (MIC). The use of MIC thwarts an active attack designed to determine the WEP key used to encrypt intercepted packets. This active attack is a combination of a bit-flipping and replay attacks, which proceed as follows:
1. A Hacker intercepts a WEP-encrypted packet.
2. The hacker flips bits in packets and recalculates ICV CRC32.
3. The hacker transmits the bit-flipped frame with known IV to the access point.
4. The access point accepts and forwards the frame because the CRC32 is correct.
5. Layer 3 device rejects the frame and sends a predictable response.
6. The access point encrypts the response and sends it to the hacker.
7. The hacker uses the response to derive the WEP key (stream cipher)
When MIC support is implemented on the root AP of a cell, all associated radio devices in that cell are instructed by the AP to start using MIC when transmitting data. No MIC configuration is required on those devices associated to the root AP. Then each device in that cell transmitting a packet adds a few bytes (the MIC) before encrypting and transmitting that packet. When the recipient receives the packet, it decrypts it and checks the MIC. If the MIC is intact and unmodified, the recipient accepts the packet. If the MIC is not intact and has been modified, the recipient discards the packet.
Because MIC is activated on the access point, not on the client device, there is no effective way to have a MIC "setting" on the workgroup bridge.
When MIC is enabled on the root access point in cell, a workgroup bridge produces and displays MIC Failed errors which do not affect the unit's functionality. These MIC errors are produced under the following conditions:
•At initial powerup and association with the root access point
•When using the root access point's HTML interface under the following scenario:
–If you wait approximately 10 minutes and then browse to the access point's Association screen and click the MAC address of an associated workgroup bridge, a MIC error is generated. This MIC error also appears on associated clients screens.
–If you wait approximately 10 minutes in the Associations screen. a MIC error is generated when you exit the screen. The MIC error also appears on the associated clients screens.
This situation is believed to be related to the access point code.
Warning Users should be aware that using MIC may reduce throughput by 80% Therefore, if throughput is an issue, users should consider not activating MIC on an access point that serves workgroup bridges.
Support for 802.1x Protocol Draft 10
Firmware version 8.80 uses 802.1x protocol draft 10. If your workgroup bridge uses Extensible Authentication Protocol (EAP) to log onto a network, the access point with which the workgroup bridge associates must use 802.1x protocol draft 10 also.
Table 1 lists firmware versions for Cisco Aironet products and the 802.1x protocol draft with which they comply.
Table 1 802.1x Protocol Drafts and Compliant Client Firmware
Firmware Version Draft 7 Draft 8 Draft 10
PC/PCI cards 4.13
PC/PCI cards 4.16
PC/PCI cards 4.23
PC/PCI cards 4.25 and later
AP34x/35x 11.05 and earlier
AP34x/35x 11.06 and later1
AP34x/35x 11.07 and later
AP34x/35x and BR35x 11.08T
1 The default draft setting in access point firmware version 11.06 and later is Draft 10.
Use the Authenticator Configuration page in access point firmware version 11.06 to select the draft of the 802.1x protocol the access point radio should use. Follow these steps to set the draft for your access point:
Step 1 Browse to the Authenticator Configuration page in the access point management system.
a. On the Summary Status page, click Setup.
b. On the Setup page, click Security.
c. On the Security Setup page, click Authentication Server.
Step 2 Use the 802.1x Protocol Version (for EAP authentication) pull-down menu to select the draft of the 802.1x protocol the access point radio should use. Menu options include:
•Draft 7—No radio firmware versions compliant with Draft 7 have LEAP capability, so you should not need to select this setting.
•Draft 8—Select this option if LEAP-enabled client devices that associate with this access point use radio firmware versions 4.13, 4.16, or 4.23, or if workgroup bridges associating with this access point use firmware version 8.58 or earlier.
•Draft 10—This is the default setting in access point and workgroup bridge firmware versions 11.06 and later. Select this option if client devices that associate with this access point or workgroup bridge use Microsoft Windows XP EAP authentication, if LEAP-enabled client devices that associate with this workgroup bridge use radio firmware version 4.25 or later, or if workgroup bridges associating with this access point use firmware version 8.65 or later.
Step 3 Click Apply or OK to apply the setting. The access point reboots.
Verify Mounting Hole Measurement
If you make a photocopy of the mounting template (included in Mounting Instructions for the Cisco Aironet Access Points, Base Stations, and Workgroup Bridges with Plastic Cases), make sure that the distance between the holes is 4 3/4 in. (12.06 cm) before you drill the holes. Some photocopy machines do not make exact duplicates of the original.
Bridge Loop May Occur with Incorrect Network Topology
If the workgroup bridge is connected to the wired LAN and is communicating with an access point on the same LAN, a network problem known as a bridge loop can occur. Avoid a bridge loop by disconnecting the workgroup bridge from the wired LAN immediately after you configure it. Figure 1 shows the network configuration in which the loop occurs.
Figure 1 Bridge Loop Caused by a Workgroup Bridge Connected to the Wired LAN
A bridge loop can also occur if two or more workgroup bridges are connected to the same remote hub. To prevent this bridge loop, always connect only one workgroup bridge to a remote hub. Figure 2 shows the network configuration in which the loop occurs.
Figure 2 Bridge Loop Caused by Two Workgroup Bridges on the Same Remote Hub
This section describes open and resolved caveats for firmware version 8.80.
Getting Bug Information on Cisco.com
If you are a Cisco.com registered user, you can use the Cisco TAC Software Bug Toolkit to identify existing bugs (or caveats) in Cisco software products. Access the TAC Software Bug Toolkit at http://www.cisco.com/support/bugtools/.
There are no open caveats associated with version 8.80. However, MIC errors are received under certain conditions that do not affect workgroup bridge functionality. For details, see the "MIC Errors" section.
The following caveats were resolved in firmware version 8.80:
•CSCdv07929—Distribute Configuration feature fails to distribute configuration to other units
•CSCdu10993—Cannot access workgroup bridge console menus or ping the device when the workgroup bridge is associated with an access point
•CSCdu811478—The workgroup bridge's web browser interface prompts you for a password on logout
For the most up-to-date, detailed troubleshooting information, refer to the Cisco TAC website at http://www.cisco.com/tac. Select Wireless LAN under Top Issues.
This section describes errors, omissions, and changes in user documentation for workgroup bridges.
Stale Out Time Setting
The workgroup bridge's management system includes a Wired LAN stale out time setting on the Configuration>Ethernet page. Use this setting to control the number of seconds the workgroup bridge continues to track a device in its association table when the device is inactive. Enter a value between 5 and 1000 seconds. (Five minutes equals 300 seconds; ten minutes equals 600 seconds.)
If the same devices are always connected to the workgroup bridge, enter 5 for the staleout time setting. If the devices connected to the workgroup bridge change frequently, enter 300 (equal to five minutes) for the staleout time setting. If you unplug the Ethernet cable from the workgroup bridge and plug it back in, the workgroup bridge removes all devices from its association table and re-learns them regardless of the stale out time setting.
Use the following documents with this document:
•Quick Start Guide: Cisco Aironet Workgroup Bridges
•Cisco Aironet Workgroup Bridge Hardware Installation Guide
•Cisco Aironet Workgroup Bridge Software Configuration Guide
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