Cisco ASR1002 Configuration Guide - Page 230

Software Redundancy on the Cisco ASR 1000 Series Routers High Availability Overview • Second IOS Process on a Cisco ASR 1002 or 1004 Router, page 4 • SSO-Aware Protocol and Applications, page 6 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 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 15. Table 15 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 Yes Router1 N/A The Cisco ASR 1001 Router only supports one RP, so dual IOS processes run on the lone RP. Cisco ASR 1002 Yes Router N/A The Cisco ASR 1002 Router only supports one RP, so dual IOS processes run on the lone RP. Cisco ASR 1004 Yes Router N/A The Cisco ASR 1004 Router only supports one RP, so dual IOS processes run on the lone RP. Cisco ASR 1006 No Router Yes The Cisco ASR 1006 Router supports a second Route Processor, so the second IOS process can only run on the standby Route Processor. 1. If a critical process, such as the ESP or the SIP fails on the Cisco ASR 1001 Router, then the entire chassis reloads. Second IOS Process on a Cisco ASR 1002 or 1004 Router For Cisco ASR 1002 and 1004 routers, Route Processor Redundancy and Stateful Switchover can be used to switch between IOS processes. RPR and SSO need to be configured by the user, however, because a second IOS process is not available by default on Cisco ASR 1002 and 1004 routers. Table 15 summarizes the software redundancy opportunities available with the second IOS process for the Cisco ASR 1002 and 1004 routers. Cisco ASR 1000 Series Aggregation Services Routers Software Configuration Guide 4