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Configuring PPP over ATM2 Encapsulation Overview


For ATM2 IQ interfaces, you can configure PPP over AAL5 encapsulation, as described in RFC 2364, PPP over AAL5. PPP over ATM encapsulation associates a PPP link with an ATM AAL5 PVC.

The Junos OS supports three PPP over ATM encapsulation types:

  • atm-ppp-llc—PPP over AAL5 LLC.

  • atm-ppp-vc-mux—PPP over ATM AAL5 multiplex.

  • atm-mlppp-llc—Multilink PPP over ATM AAL5 LLC. For this encapsulation type, your router must be equipped with a Link Services or Voice Services PIC. MLPPP over ATM encapsulation is not supported on ATM2 IQ OC48 interfaces.

To enable PPP over ATM encapsulation, include the encapsulation statement, specifying the atm-mlppp-llc, atm-ppp-llc, or atm-ppp-vc-mux encapsulation type:

You can include this statement at the following hierarchy levels:

  • [edit interfaces interface-name unit logical-unit-number]

  • [edit logical-systems logical-system-name interfaces interface-name unit logical-unit-number]

When you configure PPP over ATM encapsulation, you can enable PPP Challenge Handshake Authentication Protocol (CHAP) and keepalives on the logical interface. For more information about PPP CHAP and keepalives, see Configuring the PPP Challenge Handshake Authentication Protocol and Configuring Keepalives.


When you use PPP over ATM encapsulation, we recommend that you not include the oam-period statement in the configuration. Instead, we recommend that you enable keepalives to detect connection failures.

Example: Configuring PPP over ATM2 IQ Encapsulation

To configure three logical interfaces with PPP over ATM encapsulation:

Configuring Multilink PPP over ATM2 IQ Encapsulation

To configure multilink PPP over ATM2 IQ encapsulation: