3Com 5500-EI PWR, Справочное руководство

Страница: 354 / 1314

4-40
Examples
# Add the MTU of the interface VLAN-interface 3 to the MTU field in DD packets.
<Sysname> system-view
System View: return to User View with Ctrl+Z.
[Sysname] interface Vlan-interface 3
[Sysname-Vlan-interface3] ospf mtu-enable
ospf network-type
Syntax
ospf network-type
{
broadcast
|
nbma
|
p2mp
[
unicast
] |
p2p
}
undo ospf network-type
View
Interface view
Parameters
broadcast
: Specifies the network type as broadcast.
nbma
: Specifies the network type as NBMA.
p2mp
: Specifies the network type as point-to-multipoint.
unicast
: Sends packets to unicast addresses.
p2p
: Specifies the network type as point-to-point.
Description
Use the
ospf network-type
command to configure the network type for an interface.
Use the
undo ospf network-type
command to restore the default network type.
OSPF divides networks into four types based on link layer protocol:
z
Broadcast: If Ethernet or FDDI is adopted, OSPF 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.
z
Point-to-point (P2P): If PPP, LAPB or POS is adopted, OSPF defaults the network type to P2P.
If there is any router not supporting multicast addresses on a broadcast network, the network type of
the interface can be changed to NBMA.
For a non-broadcast multi-accessible network to be of NBMA type, any two routers in the network must
be directly reachable to each other through a virtual circuit. In other words, the network must be
fully-meshed.
For a network not meeting this condition, the network type of the interface must be changed to
point-to-multipoint. In this way, routing information can be exchanged between two routers not directly
reachable to each other through another router that is directly reachable to the two routers.
If only two routers run OSPF in the same network segment, the network type of the interface can also
be changed to point-to-point.