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Cisco ASR 1000 Series Aggregation Services Routers Software Configuration Guide
OL-16506-17
Chapter 6 High Availability Overview
Software Redundancy on the Cisco ASR 1000 Series Routers
Software Redundancy on the Cisco ASR 1000 Series Routers
This section covers the following topics:
• Software Redundancy Overview, page 6-4
• Second IOS Process on a Cisco ASR 1002 or 1004 Router, page 6-5
• SSO-Aware Protocol and Applications, page 6-7
Software Redundancy Overview
On the Cisco ASR 1000 Series Routers, IOS runs as one of many processes within the operating system.
This is different than on traditional Cisco IOS, where all processes are run within Cisco IOS. See the
“IOS as a Process” section on page 1-7 for more information regarding IOS as a process on the Cisco
ASR 1000 Series Router.
This architecture allows for software redundancy opportunities that are not available on other platforms
that run Cisco IOS software. Specifically, a standby IOS process can be available on the same Route
Processor as the active IOS process. This standby IOS process can be switched to in the event of an IOS
failure, and can also be used to upgrade subpackage software in some scenarios as the standby IOS
process in an ISSU upgrade.
On the Cisco ASR 1006 Router, the second IOS process can run only on the standby Route Processor.
Two IOS processes on the same Router Processor are not possible for any Cisco ASR 1000 Series Router
that supports dual RP hardware redundancy configurations since the second Route Processor can support
a standby IOS process. An overview of software redundancy is shown in Table 6-2.
Table 6-2 Software Redundancy Overview
Router
Support for Two IOS
Processes on Same
Route Processor
Support for a
Second IOS
Process on Standby
Route Processor Explanation
Cisco ASR 1001
Router
1
1. If a critical process, such as the ESP or the SIP fails on the Cisco ASR 1001 Router, then the entire chassis reloads.
Yes N/A The Cisco ASR 1001 Router only
supports one RP, so dual IOS processes
run on the lone RP.
Cisco ASR 1002
Router
Yes N/A The Cisco ASR 1002 Router only
supports one RP, so dual IOS processes
run on the lone RP.
Cisco ASR 1004
Router
Yes N/A The Cisco ASR 1004 Router only
supports one RP, so dual IOS processes
run on the lone RP.
Cisco ASR 1006
Router
No Yes The Cisco ASR 1006 Router supports a
second Route Processor, so the second
IOS process can only run on the
standby Route Processor.