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Hierarchy Level


Configure PPP over Ethernet-specific interface properties.

The remaining statements are explained separately. Search for a statement in CLI Explorer or click a linked statement in the Syntax section for details.

The maximum payload allowed on an Ethernet frame is 1500 bytes. For a PPPoE interface, the PPPoE header uses 6 bytes and the PPP protocol ID uses 2 bytes. This restricts the maximum MTU size on a PPPoE interface to 1492 bytes, which can cause frequent fragmentation and reassembly of larger PPP packets received over the PPPoE interface. To prevent frequent fragmentation and reassembly for PPP packets over Ethernet, you can configure the maximum transmission unit (MTU) and MRU sizes for PPP subscribers.

For PPPoE subscribers, the PPP MRU or PPP MTU size can be greater than 1492 bytes if the PPP-Max-Payload tag is received in the PPPoE Active Discovery Request (PADR) packets.

The PPP-Max-Payload option allows you to override the default behavior of the PPPoE client by providing a maximum size that the PPP payload can support in both sending and receiving directions. The PPPoE server might allow the negotiation of an MRU larger than 1492 octets and the ability to use an MTU larger than 1500 octets.

It is important to set an appropriate value for the MTU size of the physical interface before setting ppp-max-payload. The value of mtu must be greater than the value of ppp-max-payload.

To enable Jumbo frames refer Understanding Jumbo Frames Support for Ethernet Interfaces.

Required Privilege Level

interface—To view this statement in the configuration.

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

Release Information

Statement introduced before Junos OS Release 7.4.

client Statement introduced in Junos OS Release 8.5.

server Statement introduced in Junos OS Release 8.5.

ppp-max-payload Statement introduced in Junos OS Release 15.1X49-D100.