Specifications

11
Release Notes for Cisco uBR924 Cable Access Router for Cisco IOS Release 12.1(5)T
OL-0385-04 Rev. B0 (2/2001)
New and Changed Information
Parser Cache
The Parser Cache feature optimizes the parsing (translation) of Cisco IOS software configuration
command lines by remembering how to parse recently encountered command lines. This feature was
developed to improve the scalability of the Cisco IOS software command-line interface (CLI) parser
when processing large configuration files. This improvement is especially useful for those cases in
which thousands of virtual circuits must be configured for interfaces, or hundreds of access control lists
(ACLs) are required. The parser chain cache can rapidly recognize and translate configuration lines that
differ slightly from previously used configuration lines (for example, pvc 0/100, pvc 0/101, and so on).
Testing indicates an improvement to load time of between 30% and 36% for large configuration files
when using the parser cache.
The parser cache is enabled by default on all platforms using Cisco IOS Release 12.1(5)T or later. A
new global configuration command, [no] parser cache, allows the disabling or reenabling of this
feature.
No New Hardware Features in Release 12.1(3a)T1
Cisco IOS Release 12.1(3a)T1 does not contain any new hardware features for the Cisco uBR924 Cable
Access Router.
New Software Features in Release 12.1(3a)T1
The following new software features are supported by the Cisco uBR924 Cable Access Router for
Cisco IOS Release 12.1(3a)T1.
IP Address Negotiation
Cisco IOS Release 12.1(3a)T1 for Cisco uBR900 series Cable Access Routers adds support for the ip
address dhcp command on the cable interface. Previous releases used the ip address negotiated
command for this purpose, but this command is now reserved for serial interfaces. This change is
cosmetic only and does not change how the router obtains its IP address. See the “IP Address
Negotiation” section on page 18 for additional information.
HSRP Support for ICMP Redirects (CSCdp37610)
The HSRP Support for ICMP Redirects feature enables Internet Control Message Protocol (ICMP)
redirection on interfaces configured with the Hot Standby Router Protocol (HSRP).
When running HSRP, it is important to prevent hosts from discovering the interface (or real) Media
Access Control (MAC) addresses of routers in the HSRP group. If a host is redirected by ICMP to the
real MAC address of a router, and that router later fails, then packets from the host will be lost.
Previously, ICMP redirect messages were automatically disabled on interfaces configured with HSRP.
This feature now enables ICMP redirects on interfaces configured with HSRP. This functionality works
by filtering outgoing ICMP redirect messages through HSRP, where the next-hop IP address may be
changed to an HSRP virtual IP address.