Installation guide

Using GRP Redundancy for Hardware and Software Protection
GRP Redundant Processor Support 7
Note More than two GRPs installed in a chassis is not supported.
Configuration Tasks
By using GRP redundant processor support on the Cisco 12000 series router, you improve system
availability by installing two GRPs in a Cisco 12000 series router. One GRP functions as the primary
processor. The primary GRP supports all normal GRP operation. The other GRP functions as the
secondary processor. The secondary GRP monitors the primary and will take over normal GRP
operations if it detects a failure in the primary GRP.
Review the following sections before beginning the GRP redundancy configuration tasks:
• Using GRP Redundancy for Hardware and Software Protection
• Understanding System Requirements
• Configuration Tasks Overview
Using GRP Redundancy for Hardware and Software Protection
There are two common ways to use GRP redundant processor support, namely:
• Simple hardware backup
This method protects against a GRP card failure. The primary and secondary GRP cards are
configured with the same software image and configuration information. The startup-config
information on both GRPs is synchronized automatically, which ensures that the configuration
information on both GRPs remains identical.
• Software error protection
This method protects against critical Cisco IOS software errors in a particular release. The primary and
secondary GRP cards are configured with different software images, but with the same configuration
information. If you are using new or experimental Cisco IOS software, consider using
the software error
protection method.
You can also use GRP redundant processor support for advanced implementations. For example, you
can configure the GRP cards with the following:
• Similar software versions, but different configuration files
• Different software images and different configuration files
Note While other uses are possible, the configuration information in this guide focuses on simple
hardware backup and software error protection.
Understanding System Requirements
To configure GRP redundant processor operation, you must have a Cisco 12000 series router
containing one GRP processor card and a second GRP processor card available to install as the
secondary GRP.