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Known Limitations

Learn about known limitations in this release for MX Series routers.

For the most complete and latest information about known Junos OS defects, use the Juniper Networks online Junos Problem Report Search application.

General Routing

  • Upon MPC11 boot up, errors such as following could be seen, but these are harmless and do not have functional impact. PR1457655

  • Currently, IP options are not supported for egress firewall attach points, relevant supporting doc attached: Firewall Filter Match Conditions for IPv4 Traffic. The issue might occur IP-options router alert traffic not hitting the egress firewall filter. PR1490967

  • On all MX/SRX platforms, changing configuration AMS 1:1 warm-standby to load-balance or deterministic NAT might result in vmcore and cause traffic loss. PR1597386

  • When CFM Linktrace is initiated from AFT based MX line cards and platforms and no class of service classifiers and rewrite rules are configured for that interface, then the linktrace frames will not have the priority set as per the linktrace command. Example: traceroute ethernet maintenance-domain md6 maintenance-association ma6 mep 601 priority 7 In above case, the linktrace frame is expected to be sent out with priority 7 set in the PDU. If no class of service classifiers and rewrite rules are configured, the priority set in the PDU will not be same as priority configured in CLI.PR1630096

  • On bootup, a harmless error log is seen which does not have any functionality impact and is coming only during bootup due to the static arp configuration of the internal interfaces which in this case seems to be bme0. The static arp configuration are setup for IRI1 and during bootup both the REs tries to assign the IP addresses to their internal interfaces during which this log messages would have been displayed. But this eventually is resolved and internal IP addresses are assigned to the IRI1 interfaces, so you can ignore this error messages for the internal interfaces. The is mostly unused in case of Bugatti but present more due to legacy reasons. PR1642399

  • Configuring MPC11 in 4x100G and keeping peer in 400G mode, Link comes up on peer while staying down on local end. This issue is also specific to 400G-ZR optics as it has single media lane. The issue is not seen on other 400G optics supporting 4x100G mode.PR1653946

  • There will be no explicit PMB IDEEPROM Failure alarm generated in case there is a failure with the PMB IDEEPROM. PR1660089

  • The alarm string under show chassis alarms will display a generic alarm string codeFPC X PIC firmware outdated/FPC X PIC upgrade failed/FPC X PIC boot from golden. This alarm string does not contain any details of the PIC/LMIC slot, which has raised the alarm. PR1665581

  • Normal 25G on bootup or first time configuration work. In a special sequence when we move the speed from 25G to 10G on same link and back to 25G , the link doesnt come up in 25G. Due to transitioning between 10g to back 25G , there is some sequence which leaves YT in bad state, and it keeps reporting fault.PR1697272


  • Below IPC timeouts logs can be seen for statistics query to kernel(queried from cli or daemons querying internally)when there is config churn, or large number of IPCs getting exchanged between kernel and pfe in the system. if_pfe_msg_handler: pfe_peer_msg_handler error: error for msg type <type>, msg subtype <subtype>, opcode <op> and peer index <index> Default IPC timeout value in kernel for IPC statistics request is 10s. This can be incremented to larger value by setting below hidden config to avoid IPC timeout errors. # set system stats-timeout-lifetime 15 # commitPR1629930


  • With local reversion ON, there is a possibility of transit router not informing headend of RSVP disabled link when link is flapped more than once. As a workaround, remove local-reversion configuration. PR1576979

  • The automatic sorting of configuration entries does not work if defined under group. PR1637730

Network Management and Monitoring

  • Junos OS might translate the custom YANG configuration even after disabling the custom YANG package. PR1599107

Platform and Infrastructure

  • In some scenarios with MPC, major alarm and following messages are generated. This major error is triggered due to parity error, and the impacted queue might drop packets. This might impact the forwarding. To recover, reboot MPC card. PR1303489

  • On MX and EX9200 serial platforms, under Ethernet VPN (EVPN) environment, packets routed using IRB interface could not be fragmented due to media maximum transmission unit (MTU) problem. PR1522896

  • When the deactivate services rpm and deactivate routing-options rpm-tracking CLIs are applied together and then committed, some of the rpm tracked added routes are not deleted from the routing table. The issue cannot be seen using the following steps.

    • Deactivate routing-options rpm-tracking.

    • Commit the configuration then all the rpm tracked routes will be deleted.

    • If the RPM service needs to be deactivated, deactivate services rpm.

    • Commit

  • After a switchover event, when ppmd calls sendmsg system call to transmit the protocol packets, it gets blocked long enough that a few sendmsg calls cumulatively take up around 7 to 8 seconds. This indirectly impacts the BFD session because the BFD session has a Routing Engine-based detect time of 7.5 seconds to expire. PR1600684

Routing Policy and Firewall Filters

  • When a hierarchy specified in apply-path is configured in an ephemeral instance, then rpd might not be able to update the prefix-list for the configuration in ephemeral instance. PR1636390

Routing Protocols

  • When we have high scale, the Openconfig telemetry sensor /bgp-rib/ used in periodic streaming will cause high CPU usage by RPD. PR1625396

  • When routing-options transport-class fallback none is not configured - do not configure more than 10 transport-classes or advertise more than 10 distinct colors in SR-TE or FlexAlgo. PR1648490

User Interface and Configuration

  • On all Junos and Evolved platforms configured with persist-group-inheritance, which is enabled by default from Junos OS Release 19.4R3 onwards, might lead to mustd process crash in highly scaled configuration. PR1638847