Manual

Cisco IOS In Service Software Upgrade Process
How to Perform the ISSU Process
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Cisco IOS Release 12.2(28)SB
• ISSU - Remote File System—The Remote File System (RFS) versioning feature supports ISSU.
• ISSU - SNMP—SNMP supports ISSU.
• ISSU - STP—STP supports ISSU
SNMP Support for ISSU
ISSU - SNMP for SSO provides a mechanism for synchronizing the SNMP configurations and the MIBs
that support SSO from the active RP to the standby RP, assuming that both RPs are running the same
version of Cisco IOS software. This assumption is not valid for ISSU.
ISSU - SNMP provides an SNMP client that can handle ISSU transformations for the MIBs. An SNMP
client (SIC) handles ISSU for all MIBs and handles the transmit and receive functions required for ISSU.
During SNMP, a MIB is completely synchronized from the active RP to the standby RP only if the
versions of the MIB on both Cisco IOS releases are the same.
Compatibility Verification Using Cisco Feature Navigator
The ISSU application on Cisco Feature Navigator allows you to:
• Select an ISSU-capable image
• Identify which images are compatible with that image
• Compare two images and understand the compatibility level of the images (that is, compatible,
base-level compatible, and incompatible)
• Compare two images and see the client compatibility for each ISSU client
• Provide links to release notes for the image
How to Perform the ISSU Process
Unlike SSO, which is a mode of operation for the device and a prerequisite for performing ISSU, the
ISSU process is a series of steps performed while the router or switch is in operation. The steps result in
the implementation of new or modified Cisco IOS software, and have a minimal impact to traffic.
Restrictions for Performing the ISSU Process
The following list provides basic restrictions for performing the ISSU process:
• Even with ISSU, it is recommended that upgrades be performed during a maintenance window.
• The new features should not be enabled (if they require change of configuration) during the ISSU
process.
• In a downgrade scenario, if any feature is not available in the downgrade revision Cisco IOS
software image, that feature should be disabled prior to initiating the ISSU process.
The tasks in the following sections explain how to perform the ISSU process:
• Loading Cisco IOS Software on the Standby RP, page 16 (required)
• Switching to the Standby RP, page 17 (required)