Configuring Interface Encapsulation

PPP encapsulation is the default encapsulation type for physical interfaces. You need not configure encapsulation for any physical interfaces that support PPP encapsulation. If you do not configure encapsulation, PPP is used by default. For physical interfaces that do not support PPP encapsulation, you must configure an encapsulation to use for packets transmitted on the interface. For more information about physical interface encapsulation, see Configuring the Encapsulation on a Physical Interface.

You can optionally configure an encapsulation on a logical interface, which is the encapsulation used within certain packet types.

Configuring the Encapsulation on a Logical Interface

Generally, you configure an interface's encapsulation at the [edit interfaces interface-name] hierarchy level. However, for some encapsulation types, such as Frame Relay, ATM, and Ethernet virtual local area network (VLAN) encapsulations, you can also configure the encapsulation type that is used inside the Frame Relay, ATM, or VLAN circuit itself. To do this, include the encapsulation statement:

encapsulation (atm-ccc-cell-relay | atm-ccc-vc-mux | atm-tcc-vc-mux | atm-cisco-nlpid 
| atm-mlppp-llc | atm-nlpid | atm-ppp-llc | atm-ppp-vc-mux | atm-snap | atm-tcc-snap | 
atm-vc-mux | ether-over-atm-llc | ether-vpls-over-atm-llc | ethernet | frame-relay-ccc | 
frame-relay-tcc | multilink-frame-relay-end-to-end | multilink-ppp | vlan-ccc | vlan-tcc | 
vlan-vpls); 

You can include this statement at the following hierarchy levels:

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

Some of the ATM encapsulations are defined in RFC 2684, Multiprotocol Encapsulation over ATM Adaptation Layer 5.

The following restrictions apply to logical interface encapsulation:

• With the atm-nlpid, atm-cisco-nlpid, and atm-vc-mux encapsulations, you can configure the inet family only.
• With the CCC circuit encapsulations, you cannot configure a family on the logical interface.
• A logical interface cannot have frame-relay-ccc encapsulation unless the physical device also has frame-relay-ccc encapsulation.
• A logical interface cannot have frame-relay-tcc encapsulation unless the physical device also has frame-relay-tcc encapsulation. In addition, you must assign this logical interface a DLCI from 512 through 1022 and configure it as point-to-point.
• For interfaces that carry IP version 6 (IPv6) traffic, you cannot configure ether-over-atm-llc encapsulation.
• When you use ether-over-atm-llc encapsulation, you cannot configure multipoint interfaces.
• A logical interface cannot have vlan-ccc or vlan-vpls encapsulation unless the physical device also has vlan-ccc or vlan-vpls encapsulation, respectively. In addition, you must assign this logical interface a VLAN ID from 512 through 1023; if the VLAN ID is 511 or lower, it is subject to the normal destination filter lookups in addition to source address filtering. For more information, see Configuring VLAN Encapsulation.
• You can create an ATM cell-relay circuit by configuring an entire ATM physical device or an individual virtual circuit (VC). When you configure an entire device, only cell-relay encapsulation is allowed on the logical interfaces. For more information, see Configuring an ATM1 Cell-Relay Circuit.

For more information about ATM encapsulations, see Configuring ATM Interface Encapsulation.

For more information about Frame Relay encapsulations, see Configuring Frame Relay Interface Encapsulation.

For more information about multilink encapsulations, see the JUNOS Services Interfaces Configuration Guide.