Help us improve your experience.

Let us know what you think.

Do you have time for a two-minute survey?


heartbeat-tos (MX Series Virtual Chassis)


Hierarchy Level


Configure a network-specific value for the header field that defines either the type of service (ToS), traffic class (TC), or differential services (DS) octet that is transmitted in the header of a heartbeat packet.. This field is a single octet that ensures preferential delivery of heartbeat packets between Virtual Chassis member routers in a congested network. You can set the IP precedence portion of the ToS header field or the differentiated services code point (DSCP) in the DS header field in accordance with your network. When you configure a heartbeat-tos value, the software uses this octet value in the IP header for all generated Virtual Chassis heartbeat packets.

Configuring the heartbeat-tos Virtual Chassis heartbeat packets is particularly useful in congested networks or in networks with high bandwidth demands. For example, setting the appropriate heartbeat-tos value for your network design enables you to prioritize the traffic flows that transmit Virtual Chassis heartbeat packets at a higher service level than the traffic flows for traditional IP applications such as e-mail or Web browsing. During periods of network congestion, configuring the appropriate value can ensure reliable delivery of the heartbeat packets and decrease the likelihood of packet loss.

Best Practice:

To properly prioritize the traffic flows for heartbeat packets based on the network load, make sure you are using a value that is consistent with the protocol standard that was implemented in your network.


value—Network-specific value of the ToS, TC, or DS octet transmitted in Virtual Chassis heartbeat packets. Depending on your network design and protocol family implementation, the value you specify must conform to the following RFC standards:


  • IPv6 traffic class (TC) as defined in RFC 2460, Internet Protocol, Version 6 (IPv6) Specification

  • IPv4 and IPv6 Differentiated Services as defined in RFC 2474, Definition of the Differentiated Services Field (DS Field) in the IPv4 and IPv6 Headers

  • Assured forwarding per-hop behavior (PHB) as defined in RFC 2597, Assured Forwarding PHB Group

  • RFC 3260, New Terminology and Clarifications for Diffserv

  • Range: 0 through 255

  • Default: 0 (heartbeat-tos not set)

Required Privilege Level

routing—To view this statement in the configuration.

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

Release Information

Statement introduced in Junos OS Release 15.1.