Command Reference Guide

3Com Router 3000 Ethernet Family
Command Reference Guide
Chapter 3 OSPF Configuration Commands
3Com Corporation
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nbma: Changes the interface network type to Non-Broadcast Multicast Access.
p2mp: Changes the interface network type to point-to-multipoint.
p2p: Changes the interface network type to point-to-point.
Description
Use the ospf network-type command to configure the network type of OSPF interface.
Use the undo ospf network-type command to restore the default network type of the
OSPF interface.
OSPF divides networks into four types by link layer protocol:
z Broadcast: If Ethernet is adopted, OSFP defaults the network type to broadcast.
z Non-Broadcast Multi-access (nbma): If Frame Relay, ATM, HDLC or X.25 is
adopted, OSPF defaults the network type to NBMA.
z Point-to-Multipoint (p2mp): OSPF will not default the network type of any link layer
protocol to p2mp. The general undertaking is to change a partially connected
NBMA network to p2mp network if the NBMA network is not fully-meshed.
z Point-to-point (p2p): If PPP or LAPB is adopted, OSPF defaults the network type
to p2p.
If there is a router not supporting multicast address on the broadcast network, the
interface network type can be changed to NBMA. The interface network type can also
be changed from NBMA to broadcast.
A network that can be called an NBMA network or can be changed to a broadcast
network should satisfy the following condition: there is a virtual circuit directly connects
any two routers on the network. In other words, the network is full-meshed. If the
network cannot satisfy this condition, the interface network type must be changed to
point-to-multipoint. In this way, these two routers can exchange routing information via
a router directly connected with the two routers.
If there are only two routers running OSPF protocol on the same network segment, the
interface network type can be changed to point-to-point.
Note: When the network type of an interface is NBMA or it is changed to NBMA
manually, the peer command must be used to configure the neighboring point.
Related command: ospf dr-priority.
Example
# Set the interface serial1/0/0 to NBMA type.
[3Com ] interface serial1/0/0
[3Com -serial1/0/0] ospf network-type nbma