Juniper BGP - CONFIGURATION GUIDE V 11.1.X Configuration Manual page 575

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Configuring Local Cross-Connects for HDLC Layer 2 Services
You can also configure an HDLC layer 2 circuit in a local cross-connect configuration
between serial or POS interfaces within the same router.
The procedure is basically the same for configuring an HDLC layer 2 interface between
two PE routers and for a local cross-connect, with the following differences for local
cross-connects:
Use one of the following methods to create the HDLC layer 2 circuit over MPLS:
Use the mpls-relay or route interface command without the relay-format
ppp keywords. This command causes the router to signal VC-type HDLC on
the LDP session and use HDLC encapsulation. Use this command syntax if
the traffic carried on the serial or POS interface is any kind of standard HDLC
(including PPP) or Cisco HDLC.
host1(config-if)#mpls-relay 2.2.2.1 1
or
host1(config-if)#route interface tunnel mpls:tunnel-to-pe2 1
Use the mpls-relay or route interface command with the relay-format ppp
keywords. This command causes the router to signal VC-type PPP on the
LDP session and use PPP encapsulation instead of the default VC-type HDLC
signaling and HDLC encapsulation. Use this command syntax if the traffic
carried on the serial or POS interface contains actual PPP packets.
host1(config-if)#mpls-relay 2.2.2.1 1 relay-format ppp
or
host1(config-if)#route interface tunnel mpls:tunnel-to-pe2 1 relay-format ppp
(Optional) Attach an MPLS policy to the HDLC layer 2 circuit by using the mpls
policy command.
host1(config-if)#mpls policy input hdlc-policy
Configure the serial or POS interface and MPLS on the remote PE device.
The interfaces at either end of the HDLC layer 2 circuit can be different types
and have different speeds. For example, you can configure an HDLC layer 2
circuit between a serial interface on a T1 circuit and a POS interface on an OC3
circuit.
You must use the mpls-relay command instead of the route interface command
to configure a local cross-connect for HDLC layer 2 services.
You use the IP address of the local router as the value for the destination IP
address (remote address) in the mpls-relay command.
Chapter 7: Configuring Layer 2 Services over MPLS
Configuring HDLC Layer 2 Services
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