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Configuring Frame Relay Keepalives

 

By default, physical interfaces configured with High-level Data Link Control (HDLC) or Point-to-Point Protocol (PPP) encapsulation send keepalive packets at 10-second intervals. The Frame Relay term for keepalives is Local Management Interface (LMI) packets. Junos OS supports both ANSI T1.617 Annex D LMIs, ITU Q933 Annex A LMIs and Consortium LMI.

Consortium LMI is supported on all M120 routers with I-chip based FPCs and on all platforms with MPCs.

It s also supported on MX Series routers with MX-FPC2 and MX-FPC3, M320 Routers with Enhanced III FPCs, and on the following Enhanced Intelligent Queuing (IQE) PICs:

  • PB-4CHDS3-E3-IQE-BNC—Channelized DS3/E3 IQE PIC

  • PB-2CHOC3-STM1-IQE-SFP—Channelized OC3/STM1 IQE PIC with SFP

  • PB-1CHOC12-STM4-IQE-SFP—Channelized OC12/STM4 IQE PIC with SFP

  • PB-4OC3-STM1-IQE-SFP—SONET/SDH OC3/STM1 IQE PIC with SFP

  • PB-1OC12-STM4-IQE-SFP—SONET/SDH OC12/STM4 IQE PIC with SFP

  • PB-4DS3-E3-IQE-BNC—DS3/E3 IQE PIC

  • PB-4CHOC12-STM4-IQE-SFP—Channelized OC12/STM4 IQE PIC with SFP

  • PB-1CHOC48-STM16-IQE-SFP—Channelized OC48/STM16 IQE PIC with SFP

  • PC-4OC48-STM16-IQE-SFP—SONET/SDH OC48/STM16 IQE PIC with SFP

Junos OS running on MX80, MX240, MX480, and MX960 routers with the following MICs, supports Consortium LMI (C-LMI) based on the "Gang of Four" or "Consortium" standard (Section 6):

  • MIC-8OC3OC12-4OC48-SFP—8-port Clear-Channel OC3/OC12/STM-1/STM-4, 4-port Clear-Channel OC48/STM-16

  • MIC-4OC3OC12-1OC48-SFP—4-port Clear-Channel OC3/OC12/STM-1/STM-4, 1-port Clear-Channel OC48/STM-16

  • MIC-8DS3-E3—8-port Clear-Channel DS3/E3

  • MIC-8CHDS3-E3—8-port Channelized DS3/Clear-Channel E3

  • MIC-8CHOC3-4CHOC12-SFP—8-port Channelized OC3/STM-1, 4-port Channelized OC12/STM-4

  • MIC-4CHOC3-2CHOC12-SFP—4-port Channelized OC3/STM-1, 2-port Channelized OC12/STM-4

  • MIC-1CHOC48-SFP—1-port Channelized OC48/STM-16

  • MIC-1OC192-HO-VC-XFP—1-port OC192/STM64 with High Order VCAT/LCAS

For back-to-back Frame Relay connections, either disable the sending of keepalives on both sides of the connection, or configure one side of the connection as a data terminal equipment (DTE) (the default Junos OS configuration) and the other as a data circuit-terminating equipment (DCE).

If keepalives are enabled, the number of possible DLCI configurations on a multipoint or multicast connection is limited by the MTU size selected for the interface. You can increase the number of possible DLCIs by disabling keepalives.

You can calculate the available DLCIs by using the formula (MTU – 12) /5. To disable the sending of keepalives on a physical interface, include the no-keepalives statement at the [edit interfaces interface interface-name] hierarchy level:

Configuring Tunable Keepalives for Frame Relay LMI

On interfaces configured with Frame Relay connections, you can tune the keepalive settings by using the lmi statement. A Frame Relay interface can be either DCE or DTE (the default Junos OS configuration). DTE acts as a master, requesting status from the DCE part of the link. By default, Junos OS uses ANSI T1.617 Annex D LMIs.

To change the ANSI T1.617 Annex D LMIs to ITU Q933 Annex A LMIs:

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

To configure Frame Relay keepalive parameters:

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

    For example:

You can include the following statements:

  • n391dte—DTE full status polling interval. The DTE sends a status inquiry to the DCE at the interval specified by t391dte. n391dte specifies the frequency at which these inquiries expect a full status report; for example, a n391dte value of 10 specifies a full status report in response to every tenth inquiry. The intermediate inquiries ask for a keepalive exchange only. The range is from 1 through 255, with a default value of 6.

  • n392dce—DCE error threshold. The number of errors required to bring down the link, within the event-count specified by n393dce. The range is from 1 through 10, with a default value of 3.

  • n392dte—DTE error threshold. The number of errors required to bring down the link, within the event-count specified by n393dte. The range is from 1 through 10, with a default value of 3.

  • n393dce—DCE monitored event-count. The range is from 1 through 10, with a default value of 4.

  • n393dte—DTE monitored event-count. The range is from 1 through 10, with a default value of 4.

  • t391dte—DTE keepalive timer. Period at which the DTE sends out a keepalive response request to the DCE and updates status depending on the DTE error threshold value. The range is from 5 through 30 seconds, with a default value of 10 seconds.

  • t392dce—DCE keepalive timer. Period at which the DCE checks for keepalive responses from the DTE and updates status depending on the DCE error threshold value. The range is from 5 through 30 seconds, with a default value of 15 seconds.