Upgrade Setup

At this stage all the preconditions have been met. The unified ISSU process shuts down all management interfaces to the router in order to prevent changes in the configuration.

Final preparation for the upgrade phase includes the following actions:

• SNMP—The SNMP agent generates a juniSystemIssuStateChange trap with juniSystemIssuState set to upgrading to indicate that the final phase of the operation has begun. When the trap is issued with this state value, the SNMP agent stops accepting any new SNMP gets or sets and does not issue any further traps.
• CLI—Most CLI commands are disabled. Only reload, show issu, and show version commands are available to you until the service restoration phase completes. These commands are available on the console and are not available to Telnet sessions.
• External events—Externally created events from sources other than the CLI are ignored. These events typically come from user connections, RADIUS servers, SRC software and SDX software, and SNMP, and include login requests, COA requests, multicast join requests, packet mirroring requests, and so on. Logout requests are cached and processed at a later stage.
• Routing protocols—The unified ISSU process prompts you to consider raising the link costs for each routing protocol that is configured on the router. Raising the link cost for routes through the upgrading router enables neighbors to recompute better routes to those destinations. If you choose to raise the link cost, the higher costs can take some time to propagate through the network. Because the router is unable to determine when this has completed, it waits for 2 minutes before proceeding to the next step in the upgrade.

  The reason for raising the link cost is that once the upgrade of the line module control plane begins, routing protocol updates cannot be installed in the line modules until that upgrade completes. That period can be in the range 2–15 minutes. During the control plane upgrade, the routing protocols can still accept new routes and communicate with their neighbors but cannot install the routes.

• Routing protocols—The unified ISSU process prompts you to consider raising the link costs for each routing protocol that is configured on the router.

  Once the upgrade of the line module control plane begins, routing protocol updates cannot be installed in the line modules until that upgrade completes. That period can be in the range 2–15 minutes. During the control plane upgrade, the routing protocols can still accept new routes and communicate with their neighbors but cannot install the routes.

  Raising the link cost for routes through the upgrading router enables neighbors to recompute better routes to those destinations that do not pass through the upgrading router. If you choose to raise the link cost, the higher costs can take some time to propagate through the network. Because the router is unable to determine when this has completed, it waits for 2 minutes before proceeding to the next step in the upgrade.

• Unsupported line modules—Any unsupported line modules that are present are held down after the start of this phase when you can no longer gracefully exit from the unified ISSU process. The modules are held down for the duration of the in-service software upgrade and are then undergo a cold boot to the original running release.
• IGMP requests—The router cannot handle IGMP requests for channel changing for IPTV implementations.

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