Lab 5.6.1: B Channel Aggregation

Objectives:

  • Configure Cisco IOS routers to aggregate 2 B channels for a total link speed of 128kbps.

Scenario:

Configure the branch office router and central site router to dial two B channels for a total link speed of 128kbps. Use two dialer maps to dial the two phone numbers and enable PPP multilink.

Notes: 

Lab Tasks:

  1. Cable the lab as show in the diagram. Use the Adtran Atlas 550 to simulate the ISDN network.
  2. Configure the branch office router and the central site router for PPP encapsulation and CHAP authentication. Set the ISDN switch type, assign the ISDN SPIDs to the interface, and create the dialer-map entries. Configure DDR to dial the connection when any IP traffic is present.

    What would be the commands to enable DDR on the branch router to trigger a dial on any IP traffic?

    Test your DDR configuration. Ensure that you are able to dial the central site.

  3. When DDR triggers a connection, only one B channel is activated. To trigger the other B channel to come up, we need to add another dialer-map command to dial the other phone number at the central site. In some situations, the central site would have a phone company hunt group set up so the same phone number could be dialed twice. In this case, we need to dial the second phone number.

    What is the command to add the second dialer-map on the branch router?





  4. Now configure PPP multilink on the BRI interface:

    One the BranchRouter:
    BranchRouter(config)#int bri0/0
    BranchRouter(config-if)#ppp multilink
  5. Try to ping the central site router (192.168.3.2). Do both B channels come up? 



  6. We also have to define a threshold at which we dial the second B channel. In our case we will set the threshold to 1 in either direction so it immediately brings up the second B channel.

    One the BranchRouter:

    BranchRouter(config)#int bri0/0
    BranchRouter(config-if)#dialer load-threshold 1 either

  7. Now try to ping the central site router (192.168.3.2). Do both B channels come up?


  8. Look at the B channel on the BRI interface while the link is up with the show interface bri0/0:1 and show ppp multilink commands.

    Does it look like multilink is working?  Why? 

  9. Add the ppp multilink command to the central site router.

    What are the commands to do this?

  10. Try again - Look a B channel on the BRI interface while the link is up with the show interface bri0/0:1 and show ppp multilink commands.

Does it look like multilink is working now?