Frame Relay Subinterfaces Confusion

Futura

Please help me get my head round this:

I understand that when creating frame realy subinterfaces you have the option for 'point to point' or 'Multilink', 'point to point' is for putting an ip in the same range on both sides of the link and 'multilink' is for putting more than two interfaces on different routers on the same subnet. correct me if i'm wrong.

what I don't understand is this, on a point to point link why does creating subinterfaces prevent split horizon issues? does using subinterfaces stop broadcasts going over the link? and using the actual interfaces itself allow broadcasts and therefore send routing updates over the link?

Am i looking too deep into this?

I'm studying for my ICND2 and want to make sure I understand as much as possible.

Many Thanks

Futura

I think i've sussed it after much deliberation, with a Partial mesh frame relay topology, i'm thinking would not send route updates out of the serial they recieved them on, so using subinterfaces solves this issue.

fsanyee

Subinterfaces like you have a different interface for all connected router. For example when the router recieve a route information on S0/0.1, it can send that update out on evry other subinterface, because it's not the same.
With multipoint you use only one interface to connect the other routers. Updates from the other routers arrive on the same interface.