3Com 10014299 manual Ospf Configuration Example

OSPF Configuration Example 447

dial-up mode, although the PPP protocol is encapsulated on the link layer, it is still NBMA type. The peer must be specified manually. Use the ospf peer ip-addresscommand.

■If the network type is broadcast network or NBMA, at least the priority of one interface must be over 0.

■If an area is configured to a stub area, all routers connected with this area must be configured to stub areas.

■The interface type of two adjacent routers must be the same.

■If two or more areas are configured, at least one area must be configured into a backbone area (area 0).

■Make sure the backbone area is connected with all areas.

■A virtual connection cannot go through stub area.

2Global troubleshooting: If the previous steps are correct but OSPF still cannot find the remote route, check the following features of the configuration.

■If two or more areas are configured for one router, at least one area must be configured as a backbone area (the area-id of one area must be 0 or a virtual link must be configured).

As shown in the following diagram, only one area is configured on Router A and Router D and two areas are configured respectively for Router B (area0, area1) and Router C (area1, area2). One area in Router B is 0, which satisfies the requirement. However, none of the two areas in Router C is 0. In such a case, a virtual link must be set up between Router C and Router B.

Make sure area 2 and area 0 (backbone area) are connected.

Figure 151 OSPF Area Schematic Diagram

ar ea 0	ar ea 1		ar ea 2
Rout er A	Rout er B	Rout er C	Rout er D

■The virtual link cannot go through a stub area and the backbone area (area 0) cannot be configured as stub area. Therefore, if a virtual link is configured between Router B and Router C, area 1 cannot be configured as a stub area, nor can area 0. In the above diagram, only area 2 can be configured as a stub area.

■The router in the stub area (Router D) cannot receive an external route.

■Make sure the backbone areas are connected.