Frame Relay

Frame Relay is layer 2 packet-switched network protocol, it creates circuits between end-point devices:

• Switched Virtual Circuits (SVC) - Established dynamically by sending signaling messages to the network (CALL SETUP, DATA TRANSFER, IDLE, CALL TERMINATION).
• Permanent Virtual Circuits (PVCs) - preconfigured by the carrier, and after they are set up, only operate in DATA TRANSFER and IDLE modes. Note that some publications refer to PVCs as private VCs.

DLCI (data link connection identifier)

• DLCI has no significance beyond the single link
• 0 to 15 and 1,008 to 1,023 are reserved, typically the range of 16 to 1,007 is used by customers

Inverse Address Resolution Protocol (Inverse ARP) - resolves IPv4 to DLCI therefore IPv4 addresses must be available before VCs can be used. Frame Relay for IPv6 uses Inverse Neighbor Discovery (IND) to obtain a Layer 3 IPv6 address from a Layer 2 DLCI

Local Management Interface (LMI) - a definition of the messages used between the DTE (R1) and the DCE (the Frame Relay switch owned by the service provider). It is a keepalive mechanism that provides status information, every 10s pulls info from the network. LMI types are: CISCO, ANSI, Q933A

Troubleshooting

show frame-relay map
show frame-relay lmi
show interfaces serial