What's the real difference between point-to-point and multipoint int type

[teru-lei]

Hi All,

Does any body know the real difference between point-to-point and multipoint interface type? I just know that when you use point-to-point in frame-relay etc, you can not connect to two peers (so in frame-relay, you can just config 1 virtual-circuit). So I usually set the interface type to multipoint when I config subinterface. Because I think multipoint is better for the reason above. But is there any feature that point-to-point can do but multipoint can not? Thank You!

Best Regards

Teru Lei

[tepatel]

YES..point to point is for one PVC only while Point to multipoint is for more then one PVCs on a same interface. Also the difference is in how PVC gets learnt on p-to-multipoint interface.

Point-to-point subinterface : With point-to-point subinterfaces, each pair of routers has its own subnet. If you put the PVC on a point-to-point subinterface, the router assumes that there is only one point-to-point PVC configured on the subinterface. Therefore, any IP packets with a destination IP address in the same subnet are forwarded on this VC. This is the simplest way to configure the mapping and is therefore the recommended method. Use the frame-relay interface-dlci command to assign a DLCI to a specified Frame Relay subinterface.

Multipoint networks - Multipoint networks have three or more routers in the same subnet. If you put the PVC in a point-to-multipoint subinterface or in the main interface (which is multipoint by default), you need to either configure a static mapping or enable inverse Address Resolution Protocol (ARP) for dynamic mapping.

Here is the url for more detailed explanation between those two.

http://www.cisco.com/warp/public/779/smbiz/service/knowledge/wan/subifs.htm