Configuring a Point-to-Multipoint Frame Relay WAN

When it comes to the Hub and Spoke topology, the hub is most commonly deployed with a Point-to-MultiPoint interface. This lab will discuss and demonstrate the configuration and verification of multi-point frame relay interfaces.

Real World Application & Core Knowledge

So lets say you have a central office that uses a high end Cisco router such as a 7200 Series router to terminate multiple point-to-point frame-relay circuits that you have coming into the CO on a single DS3 circuit but you need each branch router to treat the circuit as if its a point-to-point circuit but be able to communicate with other branch networks through the central office router; How would you go about addressing this configuration?

The answer is quite easy and common. The configuration is referred to as a Frame Relay Hub and Spoke WAN. This type of network enables you to have a single main site/campus which terminates all the branch offices and also allows for branch to branch communication.

This lab will expose you to the new concept of Frame Relay Maps. A frame Relay map will allow you to map an IP address to a DLCI number, this makes the router send traffic that is destined towards that IP address to take the specified DLCI number in the frame relay map.

In this lab you’ll familiarize yourself with the following new command;

Command Description
frame-relay map ip x.x.x.x dlci# braodcast This command when executed in the physical serial interface or point-to-multipoint sub-interface configuration mode maps a specific IP Address to a specific DLCI. When you specify broadcast after the DLCI number this enables broadcast on that DLCI.
Interface Serial#/#.### multipoint This command when executed in global config will create a new point-to-multipoint sub-interface which can be used like a physical interface but allow for multiple multipoint interfaces on a single interface to control multiple multipoint frame-relay WAN’s. (I may need to read that part twice to understand it)
show frame-relay map This command when executed in privileged mode will display all frame-relay ip to dlci mappings, rather they are static (using the frame-relay map) command or dynamic; which are learned by Inverse ARP which will be discussed in the next lab.

Lab Prerequisites

  • If you are using GNS3 than load the Free CCNA Workbook GNS3 topology than start devices; R1, R2 and R3.
  • Establish a console session with devices R1, R2 and R3 than configure the devices respected hostname(s).
  • Configure R1’s Serial0/0 interface with the IP address of 10.54.123.1/29 and use Frame Relay encapsulation.
  • Configure R2’s Serial0/0.221 as a point-to-point sub-interface with the IP Address of 10.54.123.2/29 and the Frame Relay interface DLCI of 221
  • Configure R3’s Serial0/0.321 as a point-to-point sub-interface with the IP Address of 10.54.123.3/29 and the Frame Relay interface DLCI of 321

Lab Objectives

  • Configure R1’s Serial0/0 interface with two frame relay maps. Map R2’s Serial0/0 IP address to DLCI 122 and R3’s Serial0/0 IP Address to DLCI 123.
  • From R2 and R3 verify IP connectivity to the hub as well between the spokes.
  • Remove the previous configuration from R1’s Serial0/0 interface and create a point-to-multipoint sub-interface and configure it with the correct frame-relay maps. Verify the Frame-Relay Map statements using the show frame-relay map command
  • From R2 and R3 verify IP connectivity to the hub as well between the spokes using the new point-to-multipoint configuration on R1.

Lab Instruction

Objective 1. – Configure R1’s Serial0/0 interface with two frame relay maps. Map R2’s Serial0/0 IP address to DLCI 122 and R3’s Serial0/0 IP Address to DLCI 123.

R1 con0 is now available



Press RETURN to get started.



R1>enable
R1#configure terminal
Enter configuration commands, one per line.  End with CNTL/Z.
R1(config)#interface Serial0/0
R1(config-if)#frame-relay map ip 10.54.123.2 122 broadcast
R1(config-if)#frame-relay map ip 10.54.123.3 123 broadcast
R1(config-if)#end
R1#
%SYS-5-CONFIG_I: Configured from console by console
R1#

Objective 2. – From R2 and R3 verify IP connectivity to the hub as well between the spokes.

Note: If you’ve completed the lab prerequisites you should have full IP communications between all 3 routers as shown below;

R2#ping 10.54.123.1

Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 10.54.123.1, timeout is 2 seconds:
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 28/75/172 ms
R2##ping 10.54.123.3

Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 10.54.123.3, timeout is 2 seconds:
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 28/136/300 ms
R2#

Objective 3. – Remove the previous configuration from R1’s Serial0/0 interface and create a point-to-multipoint subinterface and configure it with the correct frame-relay maps. Verify the Frame-Relay Map statements using the show frame-relay map command

R1#configure terminal
Enter configuration commands, one per line.  End with CNTL/Z.
R1(config)#default interface Serial0/0
Building configuration...

Interface Serial0/0 set to default configuration
R1(config)#
%LINEPROTO-5-UPDOWN: Line protocol on Interface Serial0/0, changed
state to down
R1(config)#interface Serial0/0 
R1(config-if)#encapsulation frame-relay
R1(config-if)#interface serial0/0.123 multipoint
R1(config-if)#ip address 10.54.123.1 255.255.255.248
R1(config-if)#frame map ip 10.54.123.2 122 broadcast
R1(config-if)#frame map ip 10.54.123.3 123 broadcast
R1(config-subif)#end
R1#
%SYS-5-CONFIG_I: Configured from console by console
R1#show frame-relay map
Serial0/0.123 (up): ip 10.54.123.2 dlci 122(0x7A,0x1CA0), static,
              broadcast,
              CISCO, status defined, active
Serial0/0.123 (up): ip 10.54.123.3 dlci 123(0x7B,0x1CB0), static,
              broadcast,
              CISCO, status defined, active
R1#

Objective 4 – From R2 and R3 verify IP connectivity to the hub as well between the spokes using the new point-to-multipoint configuration on R1.

R2#ping 10.54.123.1

Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 10.54.123.1, timeout is 2 seconds:
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 28/75/124 ms
R2#ping 10.54.123.3

Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 10.54.123.3, timeout is 2 seconds:
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 52/121/264 ms
R2#

R3#ping 10.54.123.1

Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 10.54.123.1, timeout is 2 seconds:
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 24/83/156 ms
R3#
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