Monday, 29 August 2016

Frame Relay - Part 2

Frame Relay NBMA (Non Broadcast Multiple access )

       Non Broadcast multiple access refer of a network type where several hosts are connected. However, The data are transmitted only directly from one host to single host across the network or virtual circuit. NBMA network support broadcast and multicast traffic manually.

  NBMA is mainly employed on networks that do not have broadcast or multicast capabilities. Frame Relay, Asynchronous Transfer Mode (ATM), home power line networking, and X.25 are some common examples of NBMA network technologies.

Frame Relay is multi-access since all routers can  access the network but you are unable to send  broadcasts over the frame relay network. No broadcast also means you are unable to send multiple traffic. No multiple means you'll be in trouble with routing protocols. RIPv2, EIGRP and OSPF use multicast. Does this mean you can't use routing protocols with frame relay?

  •  OSPF and EIGRP can also use unicast instead of multicast.
  • There is a method to emulate broadcasts over your frame relay network.
In another way which type of problems we faced in frame relay and routing ? Do you remember the characteristics of distance vector routing protocols?

In this scenario I have configured EIGRP on all the routers. Router branch office 1 is sending routing information towards router customer HQ router who will store the prefix in its routing table.

 Now.. Remember ! split-horizon rule? whatever you learn from your neighbor you don't advertise back to the same interface.

We are using two PVC's but on router HQ there is still only one physical interface. Split-horizon will prevent the advertisement of routing information towards router branch office 2.

   How can we solve this problem?
  1. You can disable split-horizon (the default on physical interface)
  2. you can use sub-interface.
             In sub-interface have two method:
                 1. Point-to-point method
                 2. Point-to-multiple method
   If you use point-to-point method, it will solve your split-horizon problem but you'll need to use different IP subnet per PVC.
   If you use point-to-multipoint means you have the split-horizon problem but you can use a single IP subnet for all PVC.