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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; note that the 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. It is also supported on all platforms with MPCs.

Consortium LMI is supported on 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

• 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

To disable the sending of keepalives on a physical interface, include the no-keepalives statement at the [edit interfaces interface interface-name] hierarchy level:

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. To calculate the available DLCIs, use the formula (MTU – 12) /5. To increase the number of possible DLCIs, disable keepalives.

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 to ITU Q933 Annex A LMIs, include the lmi-type itu statement at the [edit interfaces interface-name lmi] hierarchy level:

To configure Frame Relay keepalive parameters, include the lmi statement at the [edit interfaces interface-name] hierarchy level:

• 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.