Frame Relay. CCNA4 Chapter 6. Frame Relay Overview. Layer 2 Connection-oriented Packet switched Virtual Circuits: Permanent (and Switched) Links two DTE devices through DCE Originally designed for operation over ISDN Faster than X.25 Encapsulation can be Cisco or IETF.
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CCNA4 Chapter 6
Permanent (and Switched)
RouterA(config-if)#encapsulation frame-relay ?
ietf Use RFC1490 encapsulation
RouterA(config-if)#frame-relay map ip 172.16.30.19 18
Dynamic mapping uses Inverse ARP:
DLCI = 100
What’s the next hop address for DLCI 100?
My IP address:172.16.1.2
Network performance at the router level is affected by:
Line speed of connection to the provider
Faster than CIR for a short time period
(Tc) Committed Rate measurement interval
(Bc) Committed Burst
(Be) Excess Burst – maximum transfer attempted
DE = Discard Eligibility bit. Set on oversubscribed traffic
Common: Status of virtual circuits (Keepalives)
Optional: Multicasting (DLCI 1019-1022)
Simple Flow Control
RouterA(config-if)#frame-relay lmi-type ?
Frame Relay Format
Status-enquiry message (from user device)
Status message:keepalives and PVC status
FR can divide a single physical WAN interface into multiple subinterfaces.
Subinterfaces are logical subdivisions of the physical interface.
Split-Horizon issues can be resolved.
RouterA(config-if)#int s0.1 ?
multipoint Treat as a multipoint link
point-to-point Treat as a point-to-point link
Point to Point is used when each PVC is a separate subnet.
Multipoint is used when the PVCs use the same subnet.
Configure the local DLCI for the subinterface to distinguish it from the physical interface:
RouterA(config-if)#frame-relay interface-dlci ?
<16-1007> Define a DLCI as part of the current
RouterA(config-if)#frame-relay interface-dlci 16
RouterA(config-if)# no ip address
RouterA(config-if)# encapsulation frame-relay
RouterA(config-if)# interface Serial0.102 point-to-point
RouterA(config-if)# ip address 10.1.12.1 255.255.255.0
RouterA(config-if)# frame-relay interface-dlci 102
show interface s0
show frame-relay pvc
show frame-relay map
show frame-relay lmi
Q- What is the first step in configuring Frame-Relay on an interface?
A- Setting the encapsulation
Q- What are the possible types of LMI?
A- Cisco, ANSI and Q.933a
Q- What is the solution to the issue of split-horizon when configuring multiple VCs on a single physical interface?
Q- What command can you issue to see your PVCs?
A- show frame-relay pvc
Q- What three bits does frame-relay use for congestion control?
A- FECN, BECN, DE
Q- What DLCI value defines an LMI frame?