Unified ISSU System Requirements

General Unified ISSU Considerations for All Platforms

Unified ISSU has the following caveats:

• To upgrade to Junos OS Releases 21.2R1 or 22.1R1, you need to include the no-validate option when issuing the in-service-upgrade command. The syntax for this command is request system software in-service-upgrade /var/tmp/package-name.tgz no-validate

  Junos OS releases prior to 20.4R2 do not support the no-validate option with unified ISSU. In order to upgrade from an older release to Junos OS Releases 21.2R1 or 22.1R1 with unified ISSU, you must first upgrade to a release that supports the no-validate option for unified ISSU, such as 20.4R2.

• Using unified ISSU to upgrade from an earlier Junos OS release to Junos OS Release 17.1R1 or later does not work if VPLS dynamic profiles are configured and enhanced subscriber management is not configured.

• The primary Routing Engine and backup Routing Engine must be running the same software version before you can perform a unified ISSU.

• The unified ISSU process is terminated and a message is displayed if the Junos OS version specified for installation is a version earlier than the one currently running on the device.

• The unified ISSU process is terminated if the specified upgrade has conflicts with the current configuration, components supported, and so forth.

• You cannot take PICs offline or bring them online during a unified ISSU.

• User-initiated GRES is blocked when the device is undergoing a unified ISSU.

• Unified ISSU does not support extension application packages developed with the Junos SDK.

• To downgrade from a unified ISSU-capable release to a previous software release (unified ISSU-capable or not), use the request system software add package-name command. Unlike an upgrade using the unified ISSU process, a downgrade using the request system software add package-name command can cause network disruptions and loss of data. For more information about the use of the request system software add package-name command, see the Junos OS Software Installation and Upgrade Guide.

• Unicast reverse-path-forwarding (RPF)-related statistics are not saved across a unified ISSU, and the unicast RPF counters are reset to zero during a unified ISSU.

• BGP session uptime and downtime statistics are not synchronized between the primary and backup Routing Engines during a unified ISSU. The backup Routing Engine maintains its own session uptime based on the time when the backup first becomes aware of the established sessions. For example, if the backup Routing Engine is rebooted (or if you run restart routing on the backup Routing Engine), the backup Routing Engine uptime is a short duration, because the backup has just learned about the established sessions. If the backup is operating when the BGP sessions first come up on the primary, the uptime on the primary and the uptime on the backup are almost the same duration. After a Routing Engine switchover, the new primary continues from the time left on the backup Routing Engine.

• If proxy ARP is enabled on your device, you must delete the unconditional-src-learn statement from the [edit interfaces interface-name unit 0 family inet] hierarchy level before the unified ISSU process begins and include it after the unified ISSU process is complete. Note that the unconditional-src-learn statement is not included by default.

Unified ISSU Considerations for MX Series Routers

Unified ISSU has the following caveats for MX Series routers:

• Unified ISSU for MX Series routers does not support the IEEE 802.1ag OAM and IEEE 802.3ah protocols.

• If clock synchronization is configured, the unified ISSU process terminates. For Junos OS Releases 22.1R1 and above, you can use the request system software in-service-upgrade command with the handle-incompatible-config option to automatically deactivate/activate clock synchronization for PTP and Synchronous Ethernet.

• On MX Series routers with MPC/MIC interfaces, the policers for transit traffic and statistics are disabled temporarily during the unified ISSU process.

• On MX Series MPCs, interface-specific and firewall filter statistics are preserved across a unified ISSU. During the unified ISSU, counter and policer operations are disabled.

• To preserve statistics across a unified ISSU on MX Series routers with MPC/MIC interfaces, the router stores the statistics data as binary large objects. The router collects the statistics before the unified ISSU is initialized, and restores the statistics after the unified ISSU completes. No statistics are collected during the unified ISSU process.

• After a unified ISSU operation is completed, an MPC reboot is required for MACsec to work.

• When there is a large number of subscribers configured, the Layer 2 scheduler can become oversubscribed. The unified ISSU process might terminate when the system runs out of schedulers. The system generates log messages with ISSU failures and CRC errors on the control plane. If you encounter this issue, please contact JTAC for assistance in eliminating the Layer 2 scheduler oversubscription in your configuration.

• MX Series routers support Link Aggregation Control Protocol (LACP) with fast hellos during unified ISSU. This support is disabled by default. You must enable the fast-hello-issu option on the main router and on the peer routers before starting unified ISSU. Note that the peer router must also be an MX Series router for this functionality to work.

Unified ISSU Considerations for PTX Series Routers

Unified ISSU has the following caveats for PTX Series routers:

• Link Aggregation Control Protocol (LACP) is not supported during unified ISSU on PTX Series routers. You must disable the lacp statement at the [edit interfaces interface-name aggregated-ether-options] hierarchy level before the unified ISSU process begins and enable it after the unified ISSU process is complete.

Unified ISSU Platform Support

To find out which platforms support ISSU, please use the Feature Explorer tool on the Juniper Networks website.

Unified ISSU Feature Support

Unified ISSU supports most Junos OS features starting in Junos OS Release 9.0. However, the following constraints apply:

• Link Aggregation Control Protocol (LACP)—Link changes are not processed until after the unified ISSU is complete.

• Automatic Protection Switching (APS)—Network changes are not processed until after the unified ISSU is complete.

• Ethernet Operation, Administration, and Management (OAM) as defined by IEEE 802.3ah and by IEEE 802.1ag—When a Routing Engine switchover occurs, the OAM hello message times out, triggering protocol convergence.

• Ethernet circuit cross-connect (CCC) encapsulation—Circuit changes are not processed until after the unified ISSU is complete.

• Logical systems—On devices that have logical systems configured on them, only the primary logical system supports unified ISSU.

  Note:

  When performing a unified ISSU from a FreeBSD 6.1-based Junos OS to an upgraded FreeBSD 10.x-based Junos OS, the configuration must be validated on a remote host or on a Routing Engine. The remote host or the Routing Engine must be running a Junos OS with an upgraded FreeBSD. In addition, only a few selected directories and files are preserved while upgrading from FreeBSD 6.1-based Junos OS to FreeBSD 10.x-based Junos OS. See Upgrading Junos OS with Upgraded FreeBSD.

Unified ISSU PIC Support Considerations

The following sections list information about PIC support for unified ISSU.

• PIC Considerations
• Unified ISSU Support on MX Series 3D Universal Edge Routers