Multipoint, Hub & Spoke & Point to point Framerelay

[aqusingh7]

I dont exactly understand these concepts. Has anyone a clear diagrammatic defintion with an explanation. eg/ does the multipt f.r always traverse thru a f.r switch...will all m.pt connections go thru difft or the same f.r switch to the sub i/f or i/f router? thnx

Baljit Singh

[Giuseppe Larosa]

Hello Baljit,

multipoint = a type of interface that allows one FR DTE ( a router serial interface) to reach multiple remote DTE.

simply said means that multiple DLCIs are associated to this interface.

A physical interface is multipoint in nature by definition.

Logical subinterfaces can be:

point-to-point : only one DLCI is associated to it, no problems of mapping or split horizon here.

point-to-multipoint : multiple DLCIs are associated to it, it opens the problems to mapping (which DLCI to use to reach remote site x ?).

Hub: the central site that connects directly (through a single DLCI) to each remote site.

Providers ask money for each PVC so full mesh of PVCs are not feasible.

When using point-to-point interfaces there are no mapping issues but a different IP subnet is needed for each point-to-point link.

This is not a problem when using private IP addresses RFC1918.

To implement a full mesh, or partial mesh where the hub point to multipoint interfaces can be used.

A single ip subnet is used but remote sites cannot see each other directly but only via the hub.

On multipoint mapping can be done automatically by Inverse ARP or manually by using

frame-relay map ip x.x.x.x dlci broadcast

point-to-point subinterfaces ignore inverse ARP reports.

Hope to help

Giuseppe

[Richard Burts]

Baljit

Giuseppe has provided a good explanation about multipoint and point to point Frame Relay. There is an aspect of your question that he does not address:

"eg/ does the multipt f.r always traverse thru a f.r switch...will all m.pt connections go thru difft or the same f.r switch to the sub i/f or i/f router?"

so let me address this part of your question. A router connection using Frame Relay will almost always go through a Frame Relay switch. It is possible to configure routers connected by a serial link to use Frame Relay on that link without going through a Frame Relay switch. This is sometimes done in a lab environment or perhaps a class environment. But in a live/production network a Frame Relay connection would almost always go through a Frame Relay switch.

A router serial interface could connect to a single Frame Relay switch. Any subinterface associated with that physical interface would connect to that same Frame Relay switch. It is possible for the router to connect to a different Frame Relay switch but it would require a different serial interface to connect to a different Frame Relay switch.

HTH

Rick