14 module

2Copyright © 1998, Cisco Systems, Inc.ICRC_revision_11.3

Establishing a Frame Relay PVC Connection

Chapter 14


Objectives

• Determine how Frame Relay operates

• Configure Frame Relay

• Configure Frame Relay subinterfaces

• Verify Frame Relay operation

Upon completion of this chapter, youwill be able to perform the following tasks:


Frame Relay Overview

• Virtual circuits make connections

• Connection-oriented service

DTE or CPE router

Frame Relay works here.TokenRing

CSU/DSU

DCE or FrameRelay Switch


Frame Relay Stacks

OSI Reference Model

Application

Presentation

Session

Transport

Network

Data Link

Physical

Frame Relay

IP/IPX/Apple Talk, etc

Frame Relay

EIA/TIA-232, EIA/TIA-449, V.35, X.21, EIA/TIA-530


Frame Relay Terminology

Local AccessLoop=T1

DLCI=400

DLCI=500

LMI500=Active400=Active

Local AccessLoop=64 kbps

Local AccessLoop=64 kbps


Frame Relay Address Mapping

• Get locally significant DLCIs from provider

• Map your network addresses to DLCIs

Frame Relay map

CSU/DSU

10.1.1.1

DLCI:500 PVC

Inverse ARP or

IP

(10.1.1.1)

Frame

RelayDLCI (500)


CSU/DSU

10.1.1.1

DLCI:500PVC

Frame Relay Signaling

PVCDLCI:400

Keepalive

Cisco supports three LMI standards:

• Cisco

• ANSI T1.617 Annex D

• ITU-T Q.933 Annex A

LMI

500=Active

400=Inactive


Frame Relay Operation

Frame RelayCloud

2

DLCI=100DLCI=400


3Status Inquiry

3Status Inquiry

Frame RelayCloud

2

DLCI=100DLCI=400

172.168.5.5172.168.5.7

Frame Relay Inverse ARP and LMI Operation


4DLCI 400=Active

4DLCI 100=Active

3Status Inquiry

3Status Inquiry

Frame RelayCloud

2

DLCI=100DLCI=400

172.168.5.5172.168.5.7




4DLCI 400=Active

4DLCI 100=Active

3Status Inquiry

3Status Inquiry

Frame RelayCloud

2

DLCI=100DLCI=400

172.168.5.5172.168.5.7

5 Hello, I am 172.168.5.5 on DLCI 100, who are you?


Frame Relay Map

172.168.5.5 DLCI 400 Active6

Frame RelayCloudDLCI=100

DLCI=400

Frame Relay Inverse ARP and LMI Operation (cont.)

172.168.5.5 172.168.5.7


Hello, I am 172.168.5.7 on DLCI 400.5

Frame Relay Map

172.168.5.5 DLCI 400 Active6


DLCI=400

Frame Relay Map

172.168.5.7 DLCI 100 Active6

172.168.5.7172.168.5.5



7 Hello, I am 172.168.5.5 on DLCI 100.

Hello, I am 172.168.5.7 on DLCI 400.5

6Frame Relay Map

172.168.5.5 DLCI 400 Active


DLCI=400

Frame Relay Map

172.168.5.7 DLCI 100 Active6

172.168.5.7172.168.5.5



8 Keepalive Keepalive 8


7 Hello, I am 172.168.5.5 on DLCI 100.

Hello, I am 172.168.5.7 on DLCI 400.5

6Frame Relay Map

172.168.5.5 DLCI 400 Active


DLCI=400

Frame Relay Map172.168.5.7 DLCI 100 Active6

172.168.5.7172.168.5.5


Configuring Basic Frame Relay

HQBranch

Rel. 11.2 RouterRel. 10.3 Router

interface Serial1ip address 10.16.0.1 255.255.255.0encapsulation frame-relaybandwidth 64

interface Serial1ip address 10.16.0.2 255.255.255.0encapsulation frame-relaybandwidth 64frame-relay lmi-type ansi


Configuring Basic Frame Relay (cont.)

HQBranch

Rel. 11.2 RouterRel. 10.3 Router

Inverse ARP is• enabled by default • does not appear in configuration output.

interface Serial1ip address 10.16.0.1 255.255.255.0encapsulation frame-relaybandwidth 64

interface Serial1ip address 10.16.0.2 255.255.255.0encapsulation frame-relaybandwidth 64frame-relay lmi-type ansi


Selecting a Frame Relay Topology

Star (Hub and Spoke)

Full Mesh

Partial Mesh


• Broadcast traffic must be replicated for each active connection

Reachability Issues with Routing Updates

RoutingUpdate

A

Circuit #21

Circuit #22

Circuit #23

D

C

B

B

C

D

2

3

1

Problem:


Resolving Reachability Issues

• Split horizon can cause problems in NBMA environments

• A single physical interface simulates multiple logical interfaces

• Subinterfaces can resolve split horizon issues

Subnet A

Subnet B

Subnet C

S0

PhysicalInterface

S0.1S0.2S0.3

Logical Interface


Configuring Subinterfaces

• Multipoint–Subinterfaces act as default NBMA network

–Can save subnets because uses single subnet

–Good for full-mesh topology

• Point-to-Point–Subinterfaces act as leased line

–Each point-to-point connection requires its own subnet

–Good for star or partial-mesh topologies


Configuring Subinterfaces (cont.)

RTR1

s0.2-DLCI=110

s0.3-DLCI=120

s0.1s0.2

RTR3

s0.1

s0.3RTR2

<Output Omitted>interface Serial0 no ip address encapsulation frame-relay!interface Serial0.2 point-to-point ip address 10.17.0.1 255.255.255.0 bandwidth 64 frame-relay interface-dlci 110!interface Serial0.3 point-to-point ip address 10.18.0.1 255.255.255.0 bandwidth 64 frame-relay interface-dlci 120!router rip network 10.0.0.0<output omitted>


Multipoint Subinterfaces Configuration Example

RTR1

RTR3

RTR2

RTR4

s2.1=10.17.0.2/24

s2.2=10.17.0.1/24

s2.1=10.17.0.4/24

s2.1=10.17.0.3/24


Multipoint Subinterfaces Configuration Example

<Output Omitted>!interface Serial2 no ip address encapsulation frame-relay!interface Serial2.2 multipoint ip address 10.17.0.1 255.255.255.0 bandwidth 64 frame-relay map ip 10.17.0.2 120 broadcast frame-relay map ip 10.17.0.3 130 broadcast frame-relay map ip 10.17.0.4 140 broadcast!router rip network 10.0.0.0<Output Omitted>

14 module

Education

frame relay map172

frame relay subinterfaces

frame relay switch2copyright

cisco systems

frame relay address

basic frame relay cont

basic frame relay hqbranchrel

frame relay topologystar