Lab 8.3.4: Configuring Frame Relay with Subinterfaces

Objectives:

  • Configure Frame Relay to function correctly using sub-interfaces.

Scenario:

You have been contracted by a small bank to install a Frame Relay network to connect their offices in Atlanta, Orlando, and Houston. Each office needs to connect to the other two. You have ordered Frame Relay service from a national Frame Relay service provider and have received the DLCIs in the above diagram. Routing should be handled using IGRP.

Notes: 

Lab Tasks:

  1. Cable the lab as shown in the diagram. Use the Adtran Atlas 550 to simulate the Frame Relay network. Start with a clean configuration on all routers.
  2. Configure the Ethernet interfaces on all three routers.
  3. Configure IGRP using AS# 100 on all three routers.
  4. Configure the serial interfaces that connect to the Frame Relay network for Frame Relay encapsulation and set the LMI type to ANSI.
  5. Create the sub-interfaces on each router as a point-to-point sub-interface using the DLCI number as the sub-interface number. Also, configure the Frame Relay DLCI for each sub-interface.

What command is used to assign the Frame Relay DLCI to each sub-interface?

  • On the Atlanta router:

Atlanta(config)#interface serial0/0.17 point-to-point
Atlanta(config-subif)#ip address 192.168.4.1 255.255.255.0
Atlanta(config-subif)#frame-relay interface-dlci 17
Atlanta(config)#interface serial0/0.18 point-to-point
Atlanta(config-subif)#ip address 192.168.5.1 255.255.255.0
Atlanta(config-subif)#frame-relay interface-dlci 18

  • On the Orlando router:

Orlando(config)#interface serial0/0.16 point-to-point
Orlando(config-subif)#ip address 192.168.4.2 255.255.255.0
Orlando(config-subif)#frame-relay interface-dlci 16
Orlando(config)#interface serial0/0.18 point-to-point
Orlando(config-subif)#ip address 192.168.6.1 255.255.255.0
Orlando(config-subif)#frame-relay interface-dlci 18

  • On the Houston router:

Houston(config)#interface serial0/0.16 point-to-point
Houston(config-subif)#ip address 192.168.5.2 255.255.255.0
Houston(config-subif)#frame-relay interface-dlci 16
Houston(config)#interface serial0/0.17 point-to-point
Houston(config-subif)#ip address 192.168.6.2 255.255.255.0
Houston(config-subif)#frame-relay interface-dlci 17

  1. Check your PVCs to make sure they are active with the show frame-relay pvc command. Once all of your PVCs are active, check your routing tables and connectivity. You may need to give your network a minute or so for the PVCs to become active.
  2. Examine the routing table. Notice how the routing table reflects routes to PVCs (sub-interfaces) just as it would if you had point-to-point leased line connections.
  3. What are some advantages of using point-to-point sub-interfaces in a Frame Relay network?