Hello Sims!
Although I’m sure you know most of this, let me start by stating the network types for OSPF and stating an example for each:
Point to Point - a serial connection between two routers
Broadcast - two or more routers on the same subnet connected to an Ethernet switch
The next two types of network are used to accommodate multi access technologies that don’t support broadcast. These technologies include Frame Relay and ATM.
Non Broadcast Multi Access - This is used when you have multiple routers connected on the same subnet over a non-broadcast technology such as frame relay. OSPF must emulate a broadcast by sending multiple unicast packets to all destinations. In this case, a DR must be elected and it must be the HUB router that is the DR. Otherwise OSPF will not function correctly.
Point to Multipoint - This is a network where the topology is the same as in the Non Broadcast Multi Access, however, the HUB router creates multiple point to point connections to each remote router, thus emulating multiple point to point connections. Each point to point connection has its own subnet. A DR/BDR is not necessary in this topology.
So, to specifically answer your questions:
"can you provide a non multi-access ospf network ?"
A non-multi access network is just a point to point network. Multi access just means that there are more than two routers involved in a specific topology.
" And why it is called non multi access ?"
There is no specific term “non multi access” used for OSPF network topologies. Non multi access just means point to point. If you are referring to Non Broadcast, then that just means that you are using a technology that doesn’t allow broadcasts to occur such as Frame Relay.
"The broadcast and non-broadcast network types require a DR/BDR
So which type does not require a DR/BDR ?"
Specifically, out of the four types of networks, the Broadcast network and the Non Broadcast Multi Access require DR/BDRs. The Point to Point and Point to Multipoint do not since the basis of their topologies are point to point connections. Note that in a Broadcast network the DR can be any router based on the DR elections, while in the Non Broadcast Multi Access, the DR must be the HUB router for OSPF to function.
I hope this has been helpful!
Laz