Robert E. Meyers CCNA, CCAI Youngstown State University Manager, Cisco Regional Academy Cisco Networking Academy Program Cisco Networking Academy Program Semester 4, v.2.1.2 Semester 4, v.2.1.2 Chapter 6: Frame Relay Chapter 6: Frame Relay Curriculum Review Curriculum Review Youngstown State Youngstown State University University Cisco Regional Academy Cisco Regional Academy
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Robert E. Meyers CCNA, CCAI Youngstown State University Manager, Cisco Regional Academy Cisco Networking Academy Program Semester 4, v.2.1.2 Chapter 6:
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Robert E. Meyers CCNA, CCAIYoungstown State UniversityManager, Cisco Regional Academy
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Semester 4, v.2.1.2 Semester 4, v.2.1.2
Chapter 6: Frame RelayChapter 6: Frame Relay
Curriculum ReviewCurriculum Review
Youngstown State University Youngstown State University Cisco Regional AcademyCisco Regional Academy
Robert E. Meyers CCNA, CCAIYoungstown State UniversityManager, Cisco Regional Academy
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DisclaimerDisclaimer
This presentation is intended for review purposes by Cisco Networking Academy Program teachers and students only.This presentation is not a substitute for careful study of the Cisco Academy curriculum.Most of the text and graphics have been copied directly from the on-line curriculum, and remain the copyrighted property of Cisco Systems.CCNA 640-507 objectives are used for reviews.
Robert E. Meyers CCNA, CCAIYoungstown State UniversityManager, Cisco Regional Academy
– List and describe the commands necessary for configuring basic and extended Frame Relay on subinterfaces.
– List the commands for verifying Frame Relay operation.
Robert E. Meyers CCNA, CCAIYoungstown State UniversityManager, Cisco Regional Academy
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Part 1Part 1
Frame Relay Technology
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Frame Relay OverviewFrame Relay Overview
Frame Relay provides WAN connectivity.– High performance industry-standard.– Switched data link-layer protocol.– Handles multiple virtual circuits.– Operates at the physical and data link layers of OSI.– Uses High-Level Data Link Control
(HDLC) encapsulation.– Relies on upper-layer protocols,
like TCP, for error correction.
Robert E. Meyers CCNA, CCAIYoungstown State UniversityManager, Cisco Regional Academy
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Frame Relay OverviewFrame Relay Overview
Can be a carrier-provided public network or a single network of privately owned equipment:– Data is divided into packets.– Each packet travels through a series of switches to
reach its destination.– Uses virtual circuits to
establish a connection-orientedconnection-oriented service.
Robert E. Meyers CCNA, CCAIYoungstown State UniversityManager, Cisco Regional Academy
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Important Frame Relay TermsImportant Frame Relay Terms
Access Rate– Port speed of the local loop connection.
Data-Link Connection Identifier (DLCI)– A number that identifies the FR end point.– Significant for the local network only.– Identifies logical circuits.
Robert E. Meyers CCNA, CCAIYoungstown State UniversityManager, Cisco Regional Academy
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Important Frame Relay TermsImportant Frame Relay Terms
Local Management Interface (LMI)– A signaling standard between the CPE and the
frame relay switch.– Responsible for managing the connection.
Committed Interface Rate (CIR)– The rate of service, in
bits per second, the service provider guarantees.
Robert E. Meyers CCNA, CCAIYoungstown State UniversityManager, Cisco Regional Academy
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Frame Relay OperationFrame Relay Operation
Public FR uses carrier-provided services.– Economic benefits:
• Traffic-sensitive charging rates• Telco maintains the switching equipment.
– Speeds between 56 kbps and 2 Mbps are typical.• Can support lower or
higher speeds as required.
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Frame Relay OperationFrame Relay Operation
Provides a method for multiplexing many data conversations.– Each is called a “virtual circuit.”– All are shared through one physical connection.– Multiplexing provides
high flexibility and efficient use of bandwidth.
– Users can share BW at reduced cost.
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Frame Relay DLCI’sFrame Relay DLCI’s
Permanent Virtual Circuits (PVC)– Administratively configured and managed.– Each is Identified using a DLCI number.– Significant as a local number only; are not unique in
the WAN.– Service provider's switch constructs a table mapping
DLCI values to outbound ports.
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Frame Relay FramesFrame Relay Frames
Frame format:– Flags indicate beginning and end of frame.– Address contains:
– Data – FCS (Frame Check Sequence) for data integrity.
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Frame Relay AddressingFrame Relay Addressing
DLCI address space is only 10 bits.– Possible 1024 DLCI addresses. – Usable portion of these addresses are determined
by the LMI type used.
– Cisco LMI type supports DLCI addresses from DLCI 16 to 1007 for user-data.
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Part 2Part 2
LMI: Cisco’s Implementation of Frame Relay
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LMI OperationLMI Operation
Cisco and 3 others extended the Frame Relay protocol capabilities to include Local Management Interface (LMI):– Determines the operational status of various PVC’s.– Transmits “keep alive” packets to ensure the PVC
does not shut down.– Tells the router what
PVC’s are available.
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LMI ExtensionsLMI Extensions
Eases support of large complex networks.– Virtual Circuit status messages, commoncommon:
• Synchronization between network and service.• Periodically report new or deleted PVCs.• Report on PVC integrity.
– Multicasting, optional:• Single frame multicast to numerous recipients
– Global Addressing, optional:• Gives DLCI’s global significance.• Address resolution mimics LAN method.
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LMI Frame FormatLMI Frame Format
LMI messages are sent in frames– After the flags and DLCI there are four
mandatory bytes:• Unnumbered information indicator.• Protocol discriminator.• Call reference (always all zeroes.)• Message-type field.
Robert E. Meyers CCNA, CCAIYoungstown State UniversityManager, Cisco Regional Academy
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Part 3Part 3
LMI Features
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LMI Global AddressingLMI Global Addressing
Basic (non-extended) Frame Relay supports DLCI’s that identify locally significant PVCs.– Static maps must be created to tell routers which
DLCIs to use to find a remote device.
LMI allows routers to make address translations between the DLCI and the actual device interface.– This permits routing in complex environments. – The Frame Relay network now appears to the
routers on its periphery like any LAN.
Robert E. Meyers CCNA, CCAIYoungstown State UniversityManager, Cisco Regional Academy
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MulticastingMulticasting
Multicast groups are designated by a series of four reserved DLCI values.– 1019 to 1022
– Frames sent using these DLCIs are replicated by the network and sent to all exit points in the set.
– Routing messages can be sent.
Robert E. Meyers CCNA, CCAIYoungstown State UniversityManager, Cisco Regional Academy
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Inverse ARPInverse ARP
Allows router to dynamically build a Frame Relay Map.– Learns DLCIs during LMI exchange.– Sends an Inverse ARP request to each DLCI for each
protocol configured on the interface.
– Return information is used to build the Frame Relay map.
Robert E. Meyers CCNA, CCAIYoungstown State UniversityManager, Cisco Regional Academy
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Frame Relay MapFrame Relay Map
Bind next router hop IP addresses to DLCI’s.– Static (configured by network administrator.)– Dynamic (built by router using Inverse ARP.)– Provides outgoing traffic with next-hop protocol
address, or the DLCI.
Robert E. Meyers CCNA, CCAIYoungstown State UniversityManager, Cisco Regional Academy
Configure the router with logically assigned interfaces called “subinterfaces.” – Logical “subdivisions” of a physical interface.– Each can be configured as a separate PVC.– Allows subinterface to act as a dedicated line.– Significantly reduces the cost of implementation by
reducing the actual number of router interfaces.– Subinterfaces resolve routing loops using split
horizon.• “If you learn a protocol’s route on an interface, do not send
information about that route back out that interface.”
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Subinterface: Point to PointSubinterface: Point to Point
Point to Point– A single interface is used to set up one PVC to
another on a remote router.• Both are on same subnet.
– Each point-to-point connection is its own subnet.– This solves broadcast problems.
Robert E. Meyers CCNA, CCAIYoungstown State UniversityManager, Cisco Regional Academy
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Subinterface: MultipointSubinterface: Multipoint
One subinterface is used for multiple PVC connections on multiple physical interfaces or subinterfaces on a remote router.– All participating interfaces are on the same subnet.– Each interface has its own local DLCI.– Routing updates subject to split horizon rules.
Robert E. Meyers CCNA, CCAIYoungstown State UniversityManager, Cisco Regional Academy
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Part 5Part 5
Configuration of Basic Frame Relay
Robert E. Meyers CCNA, CCAIYoungstown State UniversityManager, Cisco Regional Academy
4. Select the subinterface:router(config-if)#interface serial number.subinterface-number
[multipoint|point-to-point]
– Multipoint allows the router to forward broadcasts and updates.
5. Configure local DLCI for subinterface:router(config-f)#frame-relay interface-dlci [number]
Robert E. Meyers CCNA, CCAIYoungstown State UniversityManager, Cisco Regional Academy
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Frame Relay SummaryFrame Relay Summary
Flexible packet-switching WAN capability. Uses virtual circuits to establish connections (PVCs.) LMI’s
– Determine the operational status of the various PVCs. – Transmit keep-alive packets to ensure that the PVC does not
shut down due to inactivity. – Tell the router what PVCs are available. – Uses Inverse ARP so the router can build a Frame Relay map.– Router next-hop address determined from the routing table
must be resolved to a Frame Relay DLCI.
Can divide a single physical WAN interface into multiple subinterfaces.
Robert E. Meyers CCNA, CCAIYoungstown State UniversityManager, Cisco Regional Academy