The “frame-relay interface-dlci” command is used when we make point-to-point sub-interfaces. For point-to-point sub-interfaces, we must use this “frame-relay interface-dlci” statement. We cannot use the “frame-relay map” command. The “frame-relay map” command can be used for physical interfaces (e.g. serial 0/0) or multipoint sub-interfaces (e.g. serial 0/0.1 multipoint). We usually make use of sub-interfaces to get around the split-horizon non-advertisement problem.

NBMA is used to denote technologies like frame-relay. As an example, if we typed, “no frame-relay inverse-arp” (see Task 1 above), and then followed with a frame map statement, e.g. “frame-relay map ip 10.10.12.2 102″ without the broadcast parameter, this is an acceptable statement, i.e. . We can sent pings around, but note that ping is unicast. When we try to run our dynamic routing protocol over this NBMA (say frame-relay) network, we are not able to do so. Why? Remember that we left out the broadcast parameter of the “frame-relay map” statement. Taking RIP as an example, RIP V1 is broadcast and RIP V2 is multicast (224.0.0.9). As the names NBMA (non-broadcast multiple access) denotes, it does not work. Try comparing this with a broadcast medium e.g. Ethernet.

I hope this helps.

Thanks for the post but I have a question to sort this topic out.

1- Why do we need to assign interface DLCI when using sub interfaces? Is it because:

- ILMI doesn’t work, somehow, correctly with sub interfaces affecting automatic assignment of DLCIs from the local FR switch?

- Sub interface is by default a point to point network type, but if configured as a multipoint type, it should work fine?

What I want to know here is that: Is the physical “mutlipoint” or sub interface “multipoint” working as one BIG exiting interface which has some logical ones, and to send data using this “one big interface”, weather it’s a physical or multipoint subinterface, it should be assigned to a “small logical one” which is DLCI?

2- What is the difference between using Multipoing and NMBA in OSPF design? If the full mesh is not an issue?

Thanks for your time.