The Cisco 12000 hangs during normal operation

This is usually caused by software problems, but can also be caused by hardware. See Troubleshooting Router Hangs for this issue.

A new line card is not recognized

Use the Software Advisor (registered customers only)
tool to determine if the new card is supported in your current Cisco
IOS software version. If the LC is supported, then configure service upgrade all, save the configuration with the copy run start
command and power-cycle the router. Sometimes a reload is not
sufficient, but a power-cycle fixes the problem. If the new card is not
supported in your current Cisco IOS software version, verify that you
have enough route memory installed on the line card before upgrading
the Cisco IOS software version. For release 12.0(21)S, 256 MB of route
memory is required, especially if Border Gateway Protocol (BGP) is
configured with many peers and many routes.

The CPU utilization is running very high

While there are hardware problems that can cause this, it is much
more likely that the router is either mis-configured or something on
the network is causing the problem. See Troubleshooting High CPU Utilization on a Cisco Router to troubleshoot this issue.

Memory allocation errors are seen on the Gigabit Route Processor (GRP)

Memory allocation errors are almost never caused by hardware
problems. Troubleshooting tips for memory allocations errors are
located on the Troubleshooting Memory Problems page.

An increasing number of input drops is seen in the output of the show interfaces command

This is never due to a hardware issue with the router. See Troubleshooting Input Drops on the Cisco 12000 Series Internet Router to troubleshoot this problem.

An increasing number of ignored messages is seen in the output of the show interfaces command

One of the line cards is most likely overloaded. Follow the steps detailed in Troubleshooting Ignored Errors and No Memory Drops on the Cisco 12000 Series Internet Router.

Forwarding Information Base (FIB) error messages are seen on the GRP

Use the Cisco Error Message Decoder (registered customers only)
Tool to find information about the meaning of this error message. Some
of them point to a hardware issue on either the line card or a switch
fabric card (SFC or CSC); others indicate a Cisco IOS software bug or a
hardware issue on another part of the router. Some FIB and CEF-related
messages are explained in Troubleshooting CEF-Related Error Messages.

Inter Process-Communication (IPC)-related messages are seen on the GRP.

You can use the Cisco Error Message Decoder (registered customers only)
Tool to find information about the meaning of this error message. Some
of them point to a hardware issue on either the line card or a switch
fabric card (SFC or CSC); others indicate a Cisco IOS software bug or a
hardware issue on another part of the router. Some IPC-related messages
are explained in Cisco 12000, 10000, 7600, and 7500 Series Routers: Troubleshooting IPC-3-NOBUFF Messages.

The following error messages are seen on the GRP:

%GRP-3-FABRIC_UNI: Unicast send timed out (1)
%GRP-3-COREDUMP: Core dump incident on slot 1,
error: Fabric ping failure

Fabric ping failures occur when either a line card or the secondary
GRP fails to respond to a fabric ping request from the primary GRP over
the switch fabric. Such failures are a problem symptom that should be
investigated. You can find more information about this issue at Troubleshooting Fabric Ping Timeouts and Failures on the Cisco 12000 Series Internet Router.

The following error message is seen on the GRP:

%GRP-3-UCODEFAIL: Download failed to slot 5<br>

The image that was downloaded to the line card has been rejected by
the line card. You can try to reload the microcode using the microcode reload
configuration command. If the error message recurs, try to upgrade the
MBUS Agent ROM, MBUS Agent RAM, Fabric-downloader using the upgrade all slot command as explained in Upgrading Line Card Firmware on a Cisco 12000 Series Internet Router. You can also refer to the symptom “A new line card is not recognized” in this table.