Frame Relay Notes - LMI, Headers, and Encapsulation

Thu, 23 Jun 2011 00:00:00 +0000

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

Q933a on Aaron's Worthless Words

Frame Relay Notes - LMI, Headers, and Encapsulation