Youngstown State University Cisco Regional Academy

Curriculum Review

Semester 4, v.2.1.2 Chapter 6: Frame Relay

Robert E. Meyers

CCNA, CCAI Youngstown State University Manager, Cisco Regional Academy

Disclaimer

 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, CCAI Youngstown State University Manager, Cisco Regional Academy

Contents



Part 1: Frame Relay Technology



Part 2: LMI: Cisco’s Frame Relay



Part 3: LMI Features



Part 4: Frame Relay Subinterfaces.



Part 5: Configuration of Basic Frame Relay

Robert E. Meyers

CCNA, CCAI Youngstown State University Manager, Cisco Regional Academy

Robert E. Meyers

CCNA, CCAI Youngstown State University Manager, Cisco Regional Academy

Chapter Learning Objectives

– 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, CCAI Youngstown State University Manager, Cisco Regional Academy

Part 1 Frame Relay Technology

Robert E. Meyers

CCNA, CCAI Youngstown State University Manager, Cisco Regional Academy

Frame 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, CCAI Youngstown State University Manager, Cisco Regional Academy

Frame 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-oriented service.

Robert E. Meyers

CCNA, CCAI Youngstown State University Manager, Cisco Regional Academy

Important 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, CCAI Youngstown State University Manager, Cisco Regional Academy

Important 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, CCAI Youngstown State University Manager, Cisco Regional Academy

Frame 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.

Robert E. Meyers

CCNA, CCAI Youngstown State University Manager, Cisco Regional Academy

Frame 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.

Robert E. Meyers

CCNA, CCAI Youngstown State University Manager, Cisco Regional Academy

Frame 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.

Robert E. Meyers

CCNA, CCAI Youngstown State University Manager, Cisco Regional Academy

Frame Relay Frames

 Frame format: – Flags indicate beginning and end of frame.

– Address contains: • DLCI address (first 10 bits) • Congestion control (last 3 bits) – Data – FCS (Frame Check Sequence) for data integrity.

Robert E. Meyers

CCNA, CCAI Youngstown State University Manager, Cisco Regional Academy

Frame 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.

Robert E. Meyers

CCNA, CCAI Youngstown State University Manager, Cisco Regional Academy

Part 2 LMI: Cisco’s Implementation of Frame Relay

Robert E. Meyers

CCNA, CCAI Youngstown State University Manager, Cisco Regional Academy

LMI 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.

Robert E. Meyers

CCNA, CCAI Youngstown State University Manager, Cisco Regional Academy

LMI Extensions

 Eases support of large complex networks.

– Virtual Circuit status messages, common: • 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.

Robert E. Meyers

CCNA, CCAI Youngstown State University Manager, Cisco Regional Academy

LMI 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, CCAI Youngstown State University Manager, Cisco Regional Academy

Robert E. Meyers

CCNA, CCAI Youngstown State University Manager, Cisco Regional Academy

Part 3 LMI Features

LMI 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, CCAI Youngstown State University Manager, Cisco Regional Academy

Multicasting

 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, CCAI Youngstown State University Manager, Cisco Regional Academy

Inverse 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, CCAI Youngstown State University Manager, Cisco Regional Academy

Frame 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, CCAI Youngstown State University Manager, Cisco Regional Academy

Frame Relay Switching Tables



Consists of 4 entries:

– Incoming port and DLCI.

– Outgoing port and DLCI.

Robert E. Meyers

CCNA, CCAI Youngstown State University Manager, Cisco Regional Academy

Part 4 Frame Relay Subinterfaces

Robert E. Meyers

CCNA, CCAI Youngstown State University Manager, Cisco Regional Academy

Frame Relay Subinterfaces

 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.”

Robert E. Meyers

CCNA, CCAI Youngstown State University Manager, Cisco Regional Academy

Subinterface: 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, CCAI Youngstown State University Manager, Cisco Regional Academy

Subinterface: 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, CCAI Youngstown State University Manager, Cisco Regional Academy

Part 5 Configuration of Basic Frame Relay

Robert E. Meyers

CCNA, CCAI Youngstown State University Manager, Cisco Regional Academy

Basic Frame Relay Configuration

 Assumes that the configuration is: – On one or more physical interfaces.

– LMI and inverse ARP are supported on the remote routers .

Robert E. Meyers

CCNA, CCAI Youngstown State University Manager, Cisco Regional Academy

IOS Command Sequence

1. Select the interface: router(config)#interface serial 0 2. Configure the layer 3 address: router(config-if)#ip address [

ip|sm

] 3. Select the encapsulation type: router(config-if)#encapsulation frame-relay [

cisco|ietf

] – Use ietf when the remote router is not a Cisco router!

4. For IOS 11.1 or earlier, specify the LMI type used: router(config-if)#frame-relay lmi-type[ansi|cisco|q933a]

IOS 11.2 and later autosenses the type

.

5. Configure the link bandwidth: router(config-if)#bandwidth kilobits 6. Enable Inverse ARP(default): router(config-if)#frame-relay inverse-arp

{protocol} {dlci}

Robert E. Meyers

CCNA, CCAI Youngstown State University Manager, Cisco Regional Academy

Verifying Frame Relay Operations

 Use the following show commands: show interface • Verifies traffic on interface.

show interfaces serial • Displays the multicast DLCI, and the LMI.

show frame-relay pvc • Status of each configured connection with traffic statistics.

show frame-relay map • Displays network-layer address and associated DLCI for each remote device connected to the local router.

show frame-relay lmi • LMI traffic statistics.

Robert E. Meyers

CCNA, CCAI Youngstown State University Manager, Cisco Regional Academy

Configuring Subinterfaces

1. Select the interface.

2. Remove any network-layer addresses.

3. Configure Frame Relay encapsulation.

router(config-if)#encapsulation frame-relay 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, CCAI Youngstown State University Manager, Cisco Regional Academy

Frame 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, CCAI Youngstown State University Manager, Cisco Regional Academy

Robert E. Meyers

CCNA, CCAI Youngstown State University Manager, Cisco Regional Academy End