Help us improve your experience.

Let us know what you think.

Do you have time for a two-minute survey?

Changes in Behavior and Syntax


This section lists the changes in behavior of Junos OS features and changes in the syntax of Junos OS statements and commands from Junos OS Release 15.1R7 for the QFX Series.

Interfaces and Chassis

  • Configuring unified forwarding table profiles (EX4600 Virtual Chassis, QFX5100 Virtual Chassis, and QFX Series Virtual Chassis Fabric)—Starting in Junos OS Release 15.1R5, Packet Forwarding Engines on switches in a Virtual Chassis or Virtual Chassis Fabric (VCF) do not automatically restart upon configuring and committing a unified forwarding table profile change using the set chassis forwarding-options statement. Instead, a message is displayed at the CLI prompt and logged to the switch’s system log, prompting you to reboot the Virtual Chassis or VCF for the change to take effect. This change avoids Virtual Chassis or VCF instability that might occur with these switches if the profile update propagates to member switches and otherwise causes multiple Packet Forwarding Engines to automatically restart at the same time. This behavior change does not apply to other switch types or to EX4600 and QFX5100 switches not in a Virtual Chassis or VCF; in those cases, the switch continues to restart automatically when a unified forwarding table profile change is committed.

    We recommend that you plan to make profile changes in a Virtual Chassis or VCF comprised of these switches only when you can perform a Virtual Chassis or VCF system reboot shortly after committing the configuration update, to avoid instability if one or more member switches restart unexpectedly with the new configuration (while the remaining members are still running the old configuration).

    [See Configuring the Unified Routing Table and forwarding-options (chassis).]

  • New vc-path command display for Virtual Chassis Fabric (VCF)—Starting in Junos OS Release 15.1R5, the output from the show virtual-chassis vc-path command displays additional fields when showing the forwarding path from a source interface to a destination interface in a Virtual Chassis Fabric (VCF), including details of multiple possible next hops. The vc-path command display for a forwarding path in a Virtual Chassis remains unchanged.

    [See show virtual-chassis vc-path.]

Routing Protocols

  • Support for RFC 6996, RFC 7300, and Internet draft draft-ietf-idr-as0-06 (QFX Series)—Starting with Junos OS Release 15.1, RFC 6996, Autonomous System (AS) Reservation for Private Use, RFC 7300, Reservation of Last Autonomous System (AS) Numbers, and Internet draft draft-ietf-as0-06 are supported.

    RFC 7300, Reservation of Last Autonomous System (AS) Numbers, and the Internet draft draft-ieft-idr-as0-06 restrict the use of 2-byte AS number 65535, 4-byte AS number 4294967295UL, and AS number 0 in a configuration. When you use these restricted AS numbers, the commit operation fails.

Virtual Chassis and Virtual Chassis Fabric (VCF)

  • Adaptive load balancing (ALB) feature (Virtual Chassis Fabric)—Starting in Junos OS Release 15.1R7, the adaptive load balancing (ALB) feature for Virtual Chassis Fabric (VCF) is being deprecated to avoid potential VCF instability. The fabric-load-balance configuration statement in the [edit forwarding-options enhanced-hash-key] hierarchy is no longer available to enable and configure ALB in a VCF. When upgrading a VCF to a Junos OS release where ALB is deprecated, if the configuration has ALB enabled, you must delete the fabric-load-balance configuration item before initiating the upgrade.

    See Understanding Traffic Flow Through a Virtual Chassis Fabric and fabric-load-balance.