User's Manual

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you can configure the physical broadcasting network to be a non-broadcasting, multi-access network; you can
also configure non-broadcasting network (X.25, Frame Relay, and SMDS) to be broadcasting network. This
feature also reduces the configuration of the neighbors, for detailed information, please refer to the related
content of non-broadcasting network’s configuration of OSPF.
Configure non-broadcasting, multi-access network to be broadcasting network or non-broadcasting network,
that is, to suppose there exists virtual links from every router to other routers, or suppose they consist of a full-
mesh network. Because of the restriction of expenses, it is usually not practical; or a partially full-mesh network.
Under this situation, you can configure a point-to-multiple point network. Routers not adjacent to each other
can exchange routing information through virtual links.
OSPF point-to-multiple point interface can be defined as several point-to-point network interfaces, which
creates multiple host routes. OSPF point-to-multiple point network has the following advantages over non-
broadcasting, multi-access network and point-to-point network:
Point-to-multiple point network is easy to configure, it does not demand neighbor configuration command, it
only uses one IP and will not produce DR.
Because it does not need to full-mesh network topology, it costs less.
It is more reliable. Even when virtual links fail, it can still maintain the connection.
Under interface configuration mode, configure OSPF network type with the following command:
Command Purpose
ip ospf network
{
broadcast
|
non-
broadcast
| {
point-to-multipoint
[
non-
broadcast
] }}
This command configures the network type of OSPF.
At the end of this chapter, you can see an example of the configuration of OSPF point-to-multiple point network.
60.3.4 Configuring One-to-Multiple Broadcast Network
You do not need to describe the neighbor relations in point-to-multiple point network and broadcasting network.
But you can use command “neighbor” to describe the priority of a certain neighbor.
Before using this command, some OSPF point-to-multiple point protocol traffic is multicast traffic. So for point-
to-multiple point interface, command “neighbor” is not needed. Packet “hello”, update packet and confirmation
packet are all transmitted through broadcasting form, especially, multicast “hello” packet can dynamically
discover all neighbors.
In point-to-multiple point network, the router supposes that all neighbors have the same metric. This value can
be configured through command “ip ospf cost”. In fact, the bandwidth of every neighbor is different, so the
value should be different. This feature only applies to point-to-multiple point interface.
Using the following command to configure the interface to be point-to-multipoint interface and allocate a metric
for each neighbor:
Command Purpose
ip ospf network point-to-multipoint
On broadcasting media, configure the
interface to be a point-to-multiple point
network
Exit
Return to global configuration mode