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Configuring Keepalives

 

By default, physical interfaces configured with Cisco HDLC or PPP encapsulation send keepalive packets at 10-second intervals. The Frame Relay term for keepalives is LMI packets; the Junos OS supports both ANSI T1.617 Annex D LMIs and ITU Q933 Annex A LMIs. On ATM networks, OAM cells perform the same function. You configure OAM cells at the logical interface level; for more information, see Defining the ATM OAM F5 Loopback Cell Period.

To disable the sending of keepalives:

  1. In configuration mode, go to the [edit interfaces interface-name] hierarchy level.
  2. Include the no-keepalives statement at the [edit interfaces interface-name] hierarchy level.

To disable the sending of keepalives on a physical interface configured with Cisco HDLC encapsulation for a translational cross-connection:

  1. In configuration mode, go to the [edit interfacesinterface-name] hierarchy level.
  2. Include the no-keepalives statement with the encapsulation cisco-hdlc-tcc statement at the [edit interfaces interface-name] hierarchy level.

To disable the sending of keepalives on a physical interface configured with PPP encapsulation for a translational cross-connection:

  1. In configuration mode, go to the [edit interfaces interface-name] hierarchy level.
  2. Include the no-keepalives statement with the encapsulation ppp-tcc statement at the [edit interfaces interface-name] hierarchy level.

For more information about translation cross-connections, see Circuit and Translational Cross-Connects Overview.

When you configure PPP over ATM or Multilink PPP over ATM encapsulation, you can enable or disable keepalives on the logical interface. For more information, see Configuring PPP over ATM2 Encapsulation.

To explicitly enable the sending of keepalives:

  1. In configuration mode, go to the [edit interfaces interface-name] hierarchy level.
  2. Include the keepalives statement at the [edit interfaces interface-name] hierarchy level.

To change one or more of the default keepalive values:

  1. In configuration mode, go to the [edit interfaces interface-name] hierarchy level.
  2. Include the keepalives statement with the appropriate option as intervalseconds, down-countnumber, and the up-countnumber..

On interfaces configured with Cisco HDLC or PPP encapsulation, you can include the following three keepalive statements; note that Frame Relay encapsulation is not affected by these statements:

  • interval seconds—The time in seconds between successive keepalive requests. The range is from 1 second through 32767 seconds, with a default of 10 seconds.

  • down-count number—The number of keepalive packets a destination must fail to receive before the network takes a link down. The range is from 1 through 255, with a default of 3.

  • up-count number—The number of keepalive packets a destination must receive to change a link’s status from down to up. The range is from 1 through 255, with a default of 1.

Caution

If interface keepalives are configured on an interface that does not support the keepalives configuration statement (for example, 10-Gigabit Ethernet), the link layer may go down when the PIC is restarted. Avoid configuring the keepalives on interfaces that do not support the keepalives configuration statement.

For information about Frame Relay keepalive settings, see Configuring Frame Relay Keepalives.

On MX Series routers with Modular Port Concentrators/Modular Interface Cards (MPCs/MICs), the Packet Forwarding Engine on an MPC/MIC processes and responds to Link Control Protocol (LCP) Echo-Request keepalive packets that the PPP subscriber (client) initiates and sends to the router. The mechanism by which LCP Echo-Request packets are processed by the Packet Forwarding Engine instead of by the Routing Engine is referred to as PPP fast keepalive For more information about how PPP fast keepalive works on an MX Series router with MPCs/MICs, see the Junos OS Subscriber Access Configuration Guide.