Frame Relay
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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
Configuration
Troubleshooting
show frame-relay map show frame-relay lmi show interfaces serial