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High Availability

  • Unified ISSU with enhanced mode support (MX2008, MX2010, and MX2020 with MPC11E)—Starting in Junos OS Release 21.2R1, we support unified in-service software upgrade (ISSU) in enhanced mode. Enhanced mode runs a second copy of the Junos OS software in standby mode. The second copy is ready to take over when the software updates the old image to a new one. Enhanced mode reduces packet loss to near-zero during the ISSU process.

    Use the request system software validate in-service-upgrade package-name.tgz enhanced-mode command to verify that your device and the target release are compatible with enhanced mode. Use the request system software in-service-upgrade package-name.tgz enhanced-mode command to use unified ISSU with enhanced mode.

    [See How to Use Unified ISSU with Enhanced Mode.]

  • NSR support for RSVP-TE dynamic tunnels (MX Series and PTX Series)—Starting in Junos OS Release 21.2R1, we support nonstop active routing (NSR) for RSVP-Traffic Engineering (RSVP-TE) dynamic tunnels.

    [See Nonstop Active Routing Concepts.]

  • NSR support for SR-TE (MX Series and PTX Series)—Starting in Junos OS Release 21.2R1, we support NSR for segment routing–traffic engineering (SR-TE), allowing for hitless traffic flow on Routing Engine switchover. Routes using next hops from SR-TE policies that don't support NSR might experience traffic loss on switchover. The SR-TE policies that don't support NSR are DCSPF and Path Computation Element (PCE).

    [See Segment Routing for Traffic Engineering.]

  • Hardware-assisted inline BFD (QFX5120-32C and QFX5120-48Y)—Starting in Junos OS Release 21.2R1, we support a hardware implementation of the inline BFD protocol in firmware form. The ASIC firmware handles most of the BFD protocol processing. The firmware uses existing paths to forward any BFD events that must be processed by protocol processes. The ASIC firmware processes the packets more quickly than the software, so hardware-assisted inline BFD sessions can have keepalive intervals of less than a second. These platforms support this feature for single-hop and multihop IPv4 and IPv6 BFD sessions.

    Limitations:

    • If the Packet Forwarding Engine process restarts or the system reboots, the BFD sessions will go down.

    • When using hardware-assisted BFD with ECMP, if hardware recovery takes more time than the BFD timer, it can cause flapping in the BFD session.

    Hardware-assisted inline BFD:

    • Does not support micro BFD.
    • Is only supported on standalone devices.
    • Does not support BFD authentication.
    • Does not support IPv6 link local BFD sessions.
    • Cannot be used with VXLAN encapsulation of BFD packets.
    • Cannot be used with LAG.
    • Cannot be used with ECMP on QFX5120 Series devices.

    [See ppm and Bidirectional Forwarding Detection (BFD).]

  • Distributed and Inline BFD support for IPv6 link-local address (MX240, MX480, and MX960)—Starting in Junos OS 21.2R1, we support distribution of OSPFv3 and ISIS BFD sessions which use IPv6 link local address. To forward packets with link local ipv6 address as destination from micro-kernel, we provide next-hop id as part of the packet which the PFE uses to forward the packet on right interface. Also, we support inline mode and by default the IPv6 Link local BFD sessions will operate in inline mode. This feature is supported on MX Series MPCs 1 to 9. This is not supported on MX Series MPCs 10 and 11.

    [See Understanding Distributed BFD.]