3Com 10014299 manual By default, Ospf is disabled, Area-id, Area area-id

426CHAPTER 29: CONFIGURING OSPF

Enable OSPF and enter into the OSPF view	ospf	enable
Turn off OSPF	undo	ospf enable

By default, OSPF is disabled.

Associating an Area-idThe OSPF protocol divides the autonomous system into areas. An area is the with the Specified logical group of the router. Some routers belong to different areas (called area

Interface boundary router ABR), while a network segment can only be in one area. In other words, each interface running the OSPF protocol must be put in a specific area. The area is flagged with an area ID. The ABR transmits routing information between areas.

In addition, in the same area, all routers must agree unanimously to the parameter configurations of this area. So, in the configuration of routers in the same area, most configuration data must be considered on the basis of this area. Incorrect configurations make it impossible for adjacent routers to transfer information to each other, or can even lead to the blocking or self-loop of routing information.

Perform the following configurations in interface view.

Table 489 Associate an Area-id with the Specified Interface which runs OSPF

Operation	Command
Specify an area-id associated with the	ospf enable area	area-id
specified interface which runs OSPF
Delete an area-id associated with the	undo ospf enable	area area-id
specified interface

No area-id is associated with the specified interface by default after OSPF is enabled.

After OSPF is enabled, you must specify an area-id associated with the specified interface. OSPF only works on the specified interface.

Configuring the The OSPF protocol calculates the route on the basis of the topological structure of Network Type of the the neighboring network of this router. Each router describes the topology of its

OSPF Interface neighboring network and transmits this information to all other routers.

OSPF divides the network into 4 types according to the link layer protocols:

■When the link layer is Ethernet, OSPF regards the network type as broadcast by default.

■When the link layer protocol is frame relay, HDLC and X.25, OSPF regards the network type as NBMA by default.

■No link layer protocol is considered as point-to-multipoint type by default. It is usually manually modified from NBMA if the NBMA network is not wholly interconnected.

■When the link layer protocol is PPP, LAPB, OSPF regards the network type as point-to-point by default.

NBMA is a Non Broadcast Multi Access network. The typical network is X.25 and frame relay. Configure the poll-interval to specify the period for sending a polling