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Unified ISSU Service Restoration Phase Overview
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Application Support for Unified ISSU
Copyright © 2010, Juniper Networks, Inc.
This is the final unified ISSU phase. At this point, all three major components of the
router—the SRP modules, the line module control planes, and the line module forwarding
planes—have been upgraded and forwarding has resumed through the chassis. The
following actions take place during this phase:
The CLI is re-enabled. All commands are made available to users.
The SNMP agent is restarted and bulk statistics are collected and available for review.
(The first interval of bulk statistics collection starts when unified ISSU is still in process.
Therefore, the system performs bulk statistics collection after the first interval.)
New login requests and logout requests are processed. The router begins to accept
externally created events from sources other than the CLI and SNMP. These events
typically come from user connections, RADIUS servers, and SRC software and SDX
software, and include login requests, COA requests, multicast join requests, and so on.
Logout requests that were cached at the start of the unified in-service software upgrade
are processed.
After the flash memory on the newly active SRP module is updated, stateful SRP
switchover is available to the router.
At this point the unified in-service software upgrade is completed, and the router is
restored to normal operation. Any line modules that reloaded during the upgrade phase
and were therefore held down are now rebooted to the original running release.
Unified ISSU Phases Overview on page 107
When an application supports unified ISSU, you can configure the application on the
router and proceed with the unified in-service software upgrade with no adverse impact
to the upgrade.
Applications that do not support unified ISSU cannot maintain state and configuration
with minimal traffic loss across the upgrade. When you attempt the unified in-service
software upgrade on a router that is configured with an ISSU-challenged application,
the unified in-service software upgrade is halted and cannot proceed unless you remove
the configuration. An application that does not support high availability cannot support
unified ISSU.
Table 20 on page 116 indicates which applications support or do not support a unified
in-service software upgrade, as well as limitations on their behavior.
Chapter 5: Configuring a Unified In-Service Software Upgrade
115
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