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hold-time (Protocols IS-IS)


Hierarchy Level


Set the length of time a neighbor considers this router to be operative (up) after receiving a hello packet. If the neighbor does not receive another hello packet within the specified time, it marks this routing device as inoperative (down). The hold time itself is advertised in the hello packets.

The hold time specifies how long a neighbor should consider this routing device to be operative without receiving another hello packet. If the neighbor does not receive a hello packet from this routing device within the hold time, it marks the routing device as being unavailable.

For systems configured with graceful routing switchover (GRES) with Graceful Restart, the hold time for Primary and Backup Routing Engines should be set to a value higher than 40 seconds. This ensures that adjacencies between the Routing Engine and the neighboring peer 'helper' routers do not time out, stopping graceful restart, and all traffic.


seconds—Hold-time value, in seconds.

  • Range: 3 through 65,535 seconds, or 1 to send out hello packets every 333 milliseconds

  • Default: 9 seconds (for designated intermediate system [DIS] routers), 27 seconds (for non-DIS routers; three times the default hello interval)


When elected as a designated intermediate system [DIS] router on any LAN adjacency, the hello and hold-timer intervals are scaled down by a factor of 3. This means the default values of 9 and 27 seconds of ISIS hello and hold time intervals are scaled down to 3 and 9 seconds for LAN adjacencies. During switchovers, this hold time is too short to form LAN adjacencies. Therefore, you can configure one of the following solutions:

  • Set the hello and hold time interval for LAN adjacencies to 30 seconds and 90 seconds respectively on both the DIS router and a neighboring router.

  • Convert the LAN interfaces to point-to-point IS-IS interfaces.

The minimum hold time for point-to-point IS-IS interfaces is 27 seconds. If you assign a value lower than this, it will be automatically updated to the minimum value.

Best Practice:

On QFX10000 switches, we strongly recommend that you configure all IS-IS interfaces, including peer interfaces, as point-to-point interfaces. If you do not, you might experience session flaps, that is, IS-IS sessions that go down and then come back up, when IS-IS is configured in virtual routing and forwarding (VRF) instances. When you scale IS-IS in any scenario, you might also experience scaling issues if you do not configure IS-IS interfaces as point-to-point interfaces.

Required Privilege Level

routing—To view this statement in the configuration.

routing-control—To add this statement to the configuration.

Release Information

Statement introduced before Junos OS Release 7.4.