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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

  • When the device is up and running for a long time, there is a possibility FS gets bad blocks and it is accumulated. When any change is done to it, it reloads and tries to recover the bad blocks from the FS. PR910445

  • On the MX104 router, scheduler slip is observed when configuration changes are committed. PR1361250

  • Traffic stops after the volume limit is reached, but the traffic resumes after an aggregated Packet Forwarding Engine interface fails. PR1463723

  • For two tunnels with same TS, all traffic is forwarded on the tunnel that comes up later. PR1467364

  • LFM might flap during MX Virtual Chassis unified ISSU to and from this release. PR1516744

  • BGP neighbor flaps during the primary NG-RE reboot, although GRES or NSR is enabled. PR1524791

  • When an image with the third-party SDK upgrade (6.5.x) is installed, the CPU utilization might go up by around 5 percent. PR1534234

  • The NPC process continuously generates core files at Trinity_Ktree::Trinity_FourWayBlock, Trinity_Ktree::walkSubTree due to the next-hop memory exhaustion with the next-hop explosion. The rpd and srrd processes start hogging and the system becomes unstable. PR1538029

  • Guidelines are needed for enabling or restarting fib-streaming in low-memory conditions. PR1540478

  • Issuing the help apropos command in configuration mode is going to cause an mgd core. The mgd process will come up and as long as the command is not issued again, the core will not occur. PR1552191

  • Unified ISSU is not supported. There is a major SDK upgrade from 6.3.2 to 6.5.16, due to which the warm boot feature needed for unified ISSU is not supported by vendor. PR1554915

  • On the MX10003 routers, after a subscriber logs in, the subscriber is allowed to delete the entire AGF service stanza and commit the configurations, leaving the subscribers stuck in the Active state permanently. The user must not be allowed to delete the AGF Service configurations with active UEs. PR1555031

  • With the IPIP tunnel feature, the show dynamic-tunnels database statistics command output shows extra packet counts (that is, sampled packets when sFlow is enabled). PR1555922

  • sFlow egress sampling of MPLS packets is not supported on MX Series platforms. PR1556659

  • Resource deadlock avoided messages are observed during software add. There is no functionality impact. PR1557468

  • On the MPC11E line cards, the following error message is observed:

  • On the MPC11E line cards, the following error message is observed:

  • The rpd process generates core file if the use-for-shortcut command is configured on an SR-TE tunnel that uses an SR Algo 0 prefix SID. PR1578994

  • SyncE to PTP noise transfer passes for 400 ns p-p amplitude and frequency of 1 Hz but fails for 200 ns p-p amplitude and frequency of 0.005 Hz.PR1566291

  • G.8273.2 transient response test fails. The issue exists for legacy line cards also. PR1566354

  • With T-BC across multiple line card, average time error (cTE) test fails as there are other delays introduced causing phase variation across line cards. PR1567662

  • On deactivating aggregated Ethernet interface, we might see a traffic loss of greater than 2 seconds. This behavior is seen due to order in which the messages are processed in FPC wherein next hop change/delete is processed prior to interface down event. PR1614508

  • Spike in the rpd usage is expected because of the very large scale and OCST in general, but it does not affect any rpd functionality as telemetry streaming is the least priority task in the rpd. PR1614978


  • Junos OS Release 21.1 and earlier releases run FreeBSD version 11 whereas from Junos OS Release 21.2 onward, the FreeBSD version is 12. Software upgrade to 21.2 or later releases from 21.1 or earlier releases must use no-validate CLI option during software image upgrade process. PR1586481

  • During high route churn in scaled configurations, peer buffer becomes full and statistics request might get dropped by kernel because of their low priority as route updates are prioritized by kernel. This is a design limitation to prioritize route updates over statistics. The application is expected to retry in this scenario after route churn settled down. PR1607362

Interfaces and Chassis

  • For MC-LAG to work properly, the mc-ae interface should be configured on both the PE devices. A scenario where the mc-ae interface is deleted, deactivated, or not configured on one of the devices is a case of misconfiguration. Juniper Networks does not support such a scenario because it can lead to traffic loss and other unexpected behavior. PR1536831

  • On the MPC10 line cards, DMRs or SLRs are not received with an EVPN up MEP on the aggregated Ethernet interface with normalization. PR1543641

  • Packet loss is seen in the scaled setup with 296 LM sessions with iterator cycle time interval (100 ms). It seems there is degradation in scale number (OAM packet rate at ~5500). At this qualified PPS, now LMR packet loss is observed, but the functionality seems to be fine. To avoid LMR packet loss, reduce the scale number, and OAM packet rate should be less than 5500 PPS. PR1561397


Network Management and Monitoring

  • SNMP link up trap message is not observed after a line card reboots when scaled interfaces are present. PR1507780

  • The set system no-hidden-commands configuration blocks NETCONF sessions. As a workaround, customer can disable with the no-hidden-commands statement. PR1590350

Platform and Infrastructure

  • On MX Series platforms, under an EVPN environment, packets routed using IRB interface might not be fragmented due to media maximum transmission unit (MTU) problem. PR1522896

  • Traffic convergence is more than 50ms after disabling core-facing links on primary PE device when the core links on egress PE device are on MPC11 line card. PR1562761

Routing Protocol

  • Convergence time is high when the igmp snooping configuration is deleted. PR1550523

  • With maximum number of logical interfaces (4000 GRE tunnel per Packet Forwarding Engine) with the following configuration:

    1) family inet, associated source, and destination for each tunnel.

    2) Configure allow-fragmentation statement on one endpoint of the tunnel and configure reassemble-packets on the other endpoint of the tunnel.

    If we do deactivate chassis fpc <slot>, we might see SLIP messages while testing inline GRE reassembly feature with GRE interface scaling for MX Series. PR1581042

User Interface and Configuration

  • Unsupported options are displayed under the restart commands. PR1545558


  • In some scenario (for example, configuring firewall filter), sometimes device might show obsolete IPsec SA and NHTB entry even when the peer tear down the tunnel. PR1432925

  • Traffic loss is observed on starting the traffic with PIM disabled under the ingress primary UMH. PR1562759