To
become familiar with Frame Relay related WAN terminology
To
understand the requirements and options for Frame Relay
communications
To
simulate the configuration of a Frame Relay switch and links
between two routers
Background:
This lab focuses on the Frame Relay
Packet Switching Protocol for connecting devices on a Wide Area
Network (WAN). Frame Relay is an industry-standard, switched data
link layer protocol that handles multiple virtual circuits using
HDLC encapsulation between connected devices (routers). Frame Relay
is more efficient than X.25, the protocol for which it is generally
considered a replacement. Frame Relay is a very widely used and
important WAN communication technology. With this lab you will use a
router to create a Frame Relay switch (the cloud) and connected two
other routers through it to simulate a wide area link between two
LANs.
Point-to-Point vs. Frame Relay
Two of the most common types of WAN communication links in use today
are 1) Leased Dedicated Point-to-Point permanent circuits and 2)
Frame Relay Packet-Switched circuits. The prior labs used PPP (and
Cisco HDLC) over a (simulated) leased dedicated point-to-point
circuit. This assumes the organization that leased the circuit is
paying for the full dedicated bandwidth (such as a T1 at 1.544 Mbps)
24 hours a day, 7 days a week whether they actually use the full
bandwidth or not. Packet-switched networks enable end stations to
dynamically share the network medium (sometimes referred to as
"the cloud") and the available bandwidth and it is
possible to only pay for the bandwidth you need. This is referred to
a Committed Information Rate (CIR).
Potential Bandwidth Sharing
Frame Relay uses variable-length packets for more efficient and
flexible transfers. These packets then are switched between the
various network segments (usually phone company Central Offices or
COs) until the destination is reached. Statistical multiplexing
techniques control network access in a packet-switched network. The
advantage of this technique is that it accommodates more flexibility
and more efficient use of bandwidth especially between switches
within the cloud. Frame Relay is a way of sharing existing T-1 and
T-3 lines owned by service providers and potentially getting better
use from them. Most telephone companies now provide Frame Relay
service for customers who want connections at 56 Kbps to T-1 speeds.
Frame Relay Devices - DTE and DCE
Devices attached to a Frame Relay WAN fall into two general
categories: Data Terminal Equipment (DTE) and Data
Circuit-terminating Equipment (DCE). DTEs are typically located on
the premises of and owned by a customer. Examples of DTE devices are
terminals, personal computers, routers, and bridges. DCEs are
usually carrier-owned (phone company) internetworking devices but
can be owned by the customer. The purpose of DCE equipment is to
provide clocking and switching services in a network, which are the
devices that actually transmit data through the WAN cloud In most
cases, these are Frame Relay packet switches themselves. CSU/DSU's
are considered DCE.
The connection between a DTE device
and a DCE device consists of both a physical-layer component and a
Data link-layer component. The physical component defines the
mechanical, electrical, functional, and procedural specifications
for the connection between the devices. One of the most commonly
used physical-layer interface specifications is the Recommended
Standard (RS)-232 specification. The link-layer component defines
the protocol that establishes the connection between the DTE device,
such as a router, and the DCE device, such as a Frame Relay switch
(usually at the phone company CO).
Virtual Circuits
Frame Relay provides connection-oriented data link layer
communication. This means that a defined communication exists
between each pair of devices and that these connections are
associated with a connection identifier. This service is implemented
by using a Frame Relay virtual circuit, which is a logical
connection created between two data terminal equipment (DTE) devices
across a Frame Relay packet-switched network (PSN). Virtual circuits
provide a bi-directional communications path from one DTE device to
another and are identified by a Data-Link Connection Identifier (DLCI).
A number of virtual circuits can be
multiplexed into a single physical circuit for transmission across
the network. This capability often can reduce the equipment and
network complexity required to connect multiple DTE devices. A
virtual circuit can pass through any number of intermediate DCE
devices (switches) located within the Frame Relay PSN (Packet
Switched Network) or cloud. Frame Relay virtual circuits fall into
two categories: Switched Virtual Circuits (SVCs) and Permanent
Virtual Circuits (PVCs). PVCs are the most common.
Tools /
Preparation:
Prior to starting the lab, the
teacher or lab assistant should have at least 3 of the 5 routers in
the standard router lab available. The middle router will act as the
Frame Relay Switch and the other routers will connect through it.
The middle router must have DCE clock rate and DCE cable ends on
both serial ports (S0 and S1). Before beginning this lab you should
read the Networking Academy Second Year Companion Guide, Chapter 12
- Frame Relay. You should also review the Semester 4 On-line chapter
on Frame Relay.
Note: This is a simulated lab
since there will not likely be a real circuit with a Frame Relay
cloud available for attachment and testing of the configuration
changes made to the routers. The purpose of this lab is to practice
the process of configuring the routers to connect to a frame relay
WAN link. The following is a list of resources required.
3 Cisco routers with the IOS 11.2
or later
Middle router serial ports
connected to DCE serial cables
Hubs and/or switch attached to the
end routers
Workstation connected to each
router's console port
Select 3 routers which have WAN serial
links between them. The middle router will simulate a Frame Relay
switch and the end routers will simulate geographically separate sites
connected through the Frame Relay "cloud". This lab
worksheet uses routers Lab-A, Lab-B and Lab-C. You will configure the
two remote routers (Lab-A and Lab-C) first and then the middle Frame
Relay router (Lab B).
Step 1 - Configure the
physical 3-router setup
The two cables connected to the middle
router (Lab-B) should both be DCE in order to have this router
simulate the Frame Relay switch (The DCE cables are labeled on one
end). On router Lab-B, connect one of the DCE cables to Serial 0 and
the other to Serial 1. The DCE cable from Lab-B serial 1 will connect
to a DTE cable going to router Lab-A serial 0 and the Lab-B serial 1
cable will go to the router Lab-C DTE cable on serial 1. Use the
tables below for cabling and interfaces.
Router Frame Relay
switch
From Serial Intfc #
& Type (DCE / DTE)
To Remote Router
Name
To Serial Intf #
& Type (DCE / DTE)
Lab-B
Serial 0 / DCE
Lab-C
Serial 1 / DTE
Lab-B
Serial 1 / DCE
Lab-A
Serial 0 / DTE
Use the show
controller command to check the DCE/DTE
connections.
Lab-A#show controller S 0
What does the show
controller command for S0
indicate?
Router
Interface Ethernet
0
Interface Serial 0
Interface Serial 1
Subnet Mask
Lab-A ( remote )
192.5.5.1
201.100.11.1
Not used
255.255.255.0
Lab-B ( switch )
Not used
DLCI 21
DLCI 20
N/A
Lab-C ( remote )
223.8.151.1
Not used
201.100.11.2
255.255.255.0
Draw the 3 router set up showing cabling, interfaces, IP
addresses and DLCIs. (Hint: use the table above for the diagram)
Step 2 - Check the WAN Interface on remote
router Lab-A
Connect your workstation to the console port connection on Router
Lab-A and use
show interface
command to answer the following
questions:
Lab-A# show interface serial 0
What is the IP address and number of subnet bits for this
interface?
What is the status of the interface and the Line protocol?
What is the encapsulation currently set to?
Step 3 - Configure the Serial Interface on
Lab-A for a Frame Relay Connection
Connect your workstation to the console port connection on Router
Lab-A and use the following commands to set up Frame Relay on
interface Serial 0. Note that if your are using Cisco IOS version 11.2
or newer the Frame Relay DLCI and LMI type can be detected
automatically and will not need to be configured manually.
Lab-A - Remote Router Frame Relay Configuration
Prompt and Command
Purpose
*** Configure Interface S0 ***
Lab-A#config t
Configure from terminal
Lab-A(config)# interface Serial0
Select interface S0 to configure
Lab-A(config-if)# ip address 201.100.11.1 255.255.255.0
Set the IP address and subnet mask for S0 (use the standard router lab
IP)
Lab-A(config-if)# encapsulation frame-relay
Change the data link encapsulation from HDLC to Frame Relay. Use IETF if connecting to non-Cisco router. Default is
Cisco encapsulation.
Lab-A(config-if)# no shutdown
Bring up interface S0
exit
*** Configure Interface E0 ***
Lab-A(config)# interface Ethernet0
Select interface E0
Lab-A(config-if)# ip address 192.5.5.1 255.255.255.0
Set the IP address and subnet mask for E0 (use the standard router lab
IP)
Lab-A(config-if)# no shutdown
Bring up interface E0
exit
*** Configure IGRP
Routing Protocol ***
Lab-A(config)# router
igrp 100
Enables IGRP routing
protocol process
Lab-A(config-router)#
network 201.100.11.0
Selects network
210.100.11.0 to broadcast and receive IGRP updates
Lab-A(config-router)#
network 192.5.5.0
Selects network
192.5.5.0 to broadcast and receive IGRP updates
Control Z and Copy run start
Step 4 - Use the show
running-config interface
command to verify the configuration of S0
Lab-A#sh run
What information was displayed about Lab-A interface S0?
Step 5 - Check the WAN Interface on
remote router Lab-C
Connect your workstation to the console port connection on Router
Lab-C and use
show interface
command to answer the following
questions:
Lab-C# show interface serial 1
What is the IP address and number of subnet bits for this
interface?
What is the status of the interface and the Line protocol?
What is the encapsulation currently set to?
Step 6 - Configure the Serial Interface on
Lab-C for a Frame Relay Connection
Connect your workstation to the console port connection on Router
Lab-C and use the following commands to set up Frame Relay on
interface Serial 1. Note that if you are using Cisco IOS version
11.2 or newer the Frame Relay DLCI and LMI type can be detected
automatically.
Lab-C - Remote Router Frame Relay Configuration
Prompt and Command
Purpose
*** Configure Interface S1 ***
Lab-C#config t
Configure from terminal
Lab-C(config)# interface Serial1
Select interface S1 to configure
Lab-C(config-if)# ip address 201.100.11.2 255.255.255.0
Set the IP address and subnet mask for S1 (use the standard router lab
IP)
Lab-C(config-if)# encapsulation frame-relay
Change the data link encapsulation from HDLC to Frame Relay. Use IETF if connecting to non-Cisco router. Default is
Cisco encapsulation.
Lab-C(config-if)# no shutdown
Bring up interface S1
exit
*** Configure Interface E0 ***
Lab-C(config)# interface Ethernet0
Select interface E0
Lab-C(config-if)# ip address 223.8.151.1 255.255.255.0
Set the IP address and subnet mask for E0 (use the standard router lab
IP)
Lab-C(config-if)# no shutdown
Bring up interface E0
exit
*** Configure IGRP Routing Protocol ***
Lab-C(config)# router igrp 100
Enables IGRP routing protocol process
Lab-C(config-router)# network 201.100.11.0
Selects network 201.100.11.0 to broadcast and receive IGRP updates
Lab-C(config-router)# network 223.8.151.0
Selects network 223.8.151.0 to broadcast and receive IGRP updates
Control Z and Copy run start
Step 7 - Use the show running-config
interface command to verify the configuration of S1
Lab-C#sh run
What information was displayed about
Lab-C interface S1?
Step 8 - Configure
Lab-B as a Frame Relay Switch
Connect your workstation to the console
port on Router Lab-B and use the following commands to enable Frame
Relay switching and define interfaces Serial 0 and Serial 1 as DCE.
Lab-B - Frame Relay Switch configuration
Prompt and Command
Purpose
*** Enable Frame Relay Switching ***
Lab-B#config t
Configure from terminal
Lab-B(config)# frame-relay switching
Starts the frame relay switching process
*** Configure Interface S0 ***
Lab-B(config)# interface Serial0
Select interface E0
Lab-B(config-if)# no ip address
Specify no IP address for S0
Lab-B(config-if)# encapsulation frame-relay
Change the Layer 2 data link encapsulation from HDLC to Frame Relay.
Lab-B(config-if)# clock rate 56000
Specify the synchronous clock rate for the DCE side of the interface
Lab-B(config-if)# frame-relay intf-type dce
Specify the interface as a DCE device
Lab-B(config-if)# frame-relay route 21 interface serial 1 20
Define frame route so packets coming in on S0 DLCI 21 should go to S1
DLCI 20
Lab-B(config-if)# no shutdown
Bring up interface S0
*** Configure Interface S1 ***
Lab-B(config)# interface Serial1
Select interface S1
Lab-B(config-if)# no ip address
Specify no IP address for S1
Lab-B(config-if)# encapsulation frame-relay
Change the Layer 2 data link encapsulation from HDLC to Frame Relay.
Lab-B(config-if)# clock rate 56000
Specify the synchronous clock rate for the DCE side of the interface
Lab-B(config-if)# frame-relay intf-type dce
Specify the interface as a DCE device
Lab-B(config-if)# frame-relay route 20 interface serial 0 21
Define frame route so packets coming in on S1 DLCI 20 should go to S0
DLCI 21
Lab-B(config-if)# no shutdown
Bring up interface S0
Control Z and Copy run start
Step 9 - Use the
show running-config
interface command to verify the configuration of S0 and S1.
Note that there are several commands added by the router.
Lab-B#sh run
What information was displayed about Lab-B interface S0?
What information was displayed about Lab-B interface S1?
Step 10 - Confirm that the Line Is Up by
entering the show interface serial 0 command:
Lab-A# show interface serial 0
What is the status of the Serial frame link?
How many LMI messages were sent and received?
What does this mean?
What is the LMI type?
Step 11 - Verify the Frame Relay PVC status
for router Lab-A (remote router)
Lab-A# show frame pvc
What is the DLCI number of the connection? (DLCI=)
What is the status of the PVC? (PVC Status =)
Step 12 - Check the Frame Relay map for
router Lab-A (remote router)
Lab-A# show frame map
What is local interface number, IP address of the switch
interface and the DLCI of the connection?
What is the status of the PVC?
Step 13 - Check the LMI status for
router Lab-A (remote router)
Lab-A# show frame lmi
What is local interface number and is it DCE or DTE?
Step 14 - Verify the Frame Relay PVC
status for router Lab-B (the switch)
Lab-B# show frame pvc
What are the DLCI numbers of the connections?
What is the status of the PVCs?
Step 15 - Verify the Frame Relay routing
table for router Lab-B (the switch)
Lab-B# show frame route
What information is shown? Input intf, Input DLCI, Output Intf,
Output DLCI, Status
Step 16 - Verify the Frame Relay PVC
status for router Lab-B (the switch)