Unified ISSU Process on TX Matrix Platform

After you issue the request system software in-service-upgrade command on a TX Matrix platform, the following process occurs.

1. The management process (mgd) on the master Routing Engine of the TX Matrix platform (global master) checks whether nonstop active routing (NSR) and graceful Routing Engine switchover (GRES) are enabled in the current configuration.
2. After successful validation of nonstop active routing and graceful Routing Engine switchover configuration, the management process copies the new image to the backup Routing Engines on the TX Matrix platform and the T640 routing nodes.
3. The kernel synchronization process (ksyncd) on the backup Routing Engines synchronizes the kernel on the backup Routing Engines with that of the master Routing Engines.
4. The backup Routing Engines are upgraded with the new software and are rebooted. After rebooting, the backup Routing Engines are once again synchronized with the global master Routing Engine.
5. The unified ISSU control moves from the management process to the chassis process (chassisd). The chassis process informs the software processes about the unified ISSU and waits for responses from various software processes (such as spmb).
6. After receiving messages from the software processes indicating that the processes are ready for unified ISSU, the chassis process on the global master Routing Engine sends messages to the chassis process on the routing nodes to start the unified ISSU.
7. The chassis process on the routing nodes sends ISSU_PREPARE messages to the field replaceable units (FRUs), such as FPC and intelligent PICs.
8. On receiving an ISSU_PREPARE message, the Packet Forwarding Engines save the current state information and download the new software image from the backup Routing Engines. Next, each Packet Forwarding Engine sends ISSU_READY messages to the chassis process.
9. On receiving an ISSU_READY message from the Packet Forwarding Engines, the chassis process sends an ISSU_REBOOT message to the FRUs. While the upgrade is in progress, the FRUs keep sending ISSU_IN_PROGRESS messages to the chassis process on the routing nodes. The chassis process on each routing node, in turn, sends an ISSU_IN_PROGRESS message to the chassis process on the global master Routing Engine.
10. After the reboot, the Packet Forwarding Engines restore the saved state information and connect back to the routing nodes; the chassis process on each routing node sends an ISSU_READY message to the chassis process on the global master Routing Engine. The ISSU_READY message from the chassis process on the routing nodes indicates that the unified ISSU is complete on the FRUs.
11. The unified ISSU control moves back to the management process on the global master Routing Engine.
12. The management process initiates Routing Engine switchover on the master Routing Engines.
13. Routing Engine switchover occurs on the TX Matrix platform and the T640 routing nodes.

    Note: Currently, the FRUs on a TX Matrix platform do not support graceful Routing Engine switchover and are rebooted every time graceful Routing Engine switchover occurs.

14. After the switchover, the FRUs connect to the new master Routing Engines, and the chassis manager and PFE manager on the T640 routing node FRUs connect to the new master Routing Engines on the T640 routing nodes.
15. The management process on the global master Routing Engine initiates the upgrade process on the old master Routing Engines on the T640 routing nodes.
16. After the old master Routing Engines on the T640 routing nodes are upgraded, the management process initiates the upgrade of the old global master Routing Engine, that is, the old master Routing Engine on the TX Matrix platform.
17. After a successful unified ISSU, the TX Matrix platform and the T640 routing nodes are rebooted.