Frame Relay Notes - LMI, Headers, and Encapsulation
Local Management Interface
- Manages link between the router and frame relay switch
- Routers send Status Enquiry to the switch
- The switch responds with a Status message informing the router of the DLCIs available
- Serves as a keepalive
- Default keepalive is 10 seconds, 3 misses is failed
- Three types
- cisco <- default
- ansi (Annex D)
- q933a
R1(config)#interface s1/0 R1(config-if)#frame-relay lmi-type ansi
Headers and Encapsulation
- Link Access Procedure for Frame-mode Bearer Services (LAPF) is the first header
- Includes DLCI, DE, FECN, BECN
- To be read by the frame relay switch
- Frame relay encapsulation header is next
- To be read by the router on the other end of the VC
- Two types
- cisco : proprietary <- default
- ietf : IETF RFC 2427
R1(config)#interface s1/0 R1(config-if)#frame-relay encapsulation ietf <- for all DLCIs - or - R1(config-if)#frame-relay interface-dlci 100 ietf <- for specific DLCIs - or - R1(config-if)#frame-relay map ip 10.0.0.1 ietf <- for specific DLCis