Junos Router | Serial Interface with Frame Relay

Frame Relay is a Layer 2 encapsulation that enables the connection of your LAN via a WAN connection to a Frame Relay node. Frame Relay creates a tunnel called a permanent virtual circuit (PVC) over a private or leased line to provide connectivity to other sites over the Internet service provider's (ISP's) infrastructure. With the emergence of DSL and IP-based networks, Frame Relay is not often seen anymore, except in rural areas as a cheaper, "always on" connection.

To establish a Frame Relay connection with the Frame Relay node, the proper encapsulation of frame-relay (RFC 1490) must be configured as well as the local circuit identifier for the PVC represented by the logical property of a dlci number:

se-1/0/0 {    encapsulation frame-relay;    unit 645 {        description "to R3";        dlci 645;        family inet {            address 172.17.24.130/30;        }    }}

The router can also support back-to-back router connections by configuring one router to operate in DCE mode or by turning off keepalives on each router. If keepalives are disabled, the router will not wait for any local management messages to enable that interface. Also, turning keepalives off can help in troubleshooting by allowing for loopback testing, which we'll discuss later in this chapter.