Specifications

19
Release Notes for Cisco uBR924 Cable Access Router for Cisco IOS Release 12.1(5)T
OL-0385-04 Rev. B0 (2/2001)
Limitations and Restrictions
Upgrading Software Images Using BPI
To enable BPI encryption, the Cisco uBR924 Cable Access Router must use a Cisco IOS image that
supports BPI encryption. If the router's current software image does not support BPI encryption (or if
the current software image is corrupted), you must disable BPI encryption in the DOCSIS configuration
file and reset the router before you will be able to download a new software image.
Using Access Lists with IPSec Images
Access lists 100 and 101 should never be manually configured on the Cisco uBR924 Cable Access
Router. Configuring these access lists with Cisco IOS Release 12.1 T images that support any form of
IPSec encryption can crash the router. Use any access lists 102 through 199 instead. See the description
of caveats CSCdr45850 and CSCdr46128 on page 28 for more information.
Using Multiple PCs with the Cisco uBR924 Cable Access Router
The “MAX CPE” parameter in a Cisco uBR924 Cable Access Router’s DOCSIS configuration file
determines how many PCs (or other customer premises equipment [CPE] devices) are supported by the
Cisco uBR924 Cable Access Router. The default value for the “MAX CPE” parameter is 1, which
means only one PC can be connected to the Cisco uBR924 Cable Access Router.
The DOCSIS 1.0 specification states that a CMTS cannot age out MAC addresses for CPE devices, so
the first PC that is connected to the Cisco uBR924 Cable Access Router is normally the only one that
the CMTS recognizes as valid. If a subscriber replaces an existing PC or changes its network interface
card (NIC) to one that has a different MAC address, the CMTS will refuse to let the PC come online
because this would exceed the maximum number of CPE devices specified by the “MAX CPE”
parameter. A similar thing would happen if a user decides to move a PC from one Cisco uBR924 router
to another.
To allow a subscriber to replace an existing PC or NIC, the following workarounds are possible:
• If using a Cisco uBR7200 series router as the CMTS, enter the clear cable host MAC address
command on the Cisco uBR7200 series router to remove the PC’s MAC address from the router’s
internal address tables. The new PC will be rediscovered and associated with the correct
Cisco uBR924 Cable Access Router during the next DHCP lease cycle.
• Increase the value of the “MAX CPE” parameter in the Cisco uBR924 Cable Access Router’s
DOCSIS configuration file so that it can accommodate the desired number of PCs. Reset the
Cisco uBR924 Cable Access Router to force it to load the new configuration file.
Using the Reset Switch
The reset switch on the back panel of the Cisco uBR924 Cable Access Router is recessed to prevent
accidental resets of the router. To depress the switch, use a blunt object, such as a pen or pencil point;
do not use a sharp object, such as a knife or awl, because this could damage the switch and the router’s
circuitry.