3Com 10014299 Configure Route Summarization Within Ospf Domain, Area-id advertise notadvertise

434CHAPTER 29: CONFIGURING OSPF

which reduces the LSDB in other areas. The configuration of range is only effective when it is configured on teh ABR in the stub area.

For example, there are two network segments in an area as follows:

202.38.160.0 255.255.255.0

202.38.180.0 255.255.255.0

They are summarized into one network segment: 202.38.0.0 255.255.0.0

When the summary network segment of a specific network is added to an area, the internal routes with the IP addresses that fall in this summary network segment are not broadcast separately to other areas. Only the abstract information of the route of the whole summary network segment is broadcast. If the network segment range is restricted with the notadvertise attribute, the abstract information to this network segment route is not broadcast. This network segment is described in the form of an IP address/mask. Receiving the summary network segment and the restriction of the network segment can reduce the inter-area routing information.

Note that the route summary is only effective when configured on an ABR.

Perform the following configurations in OSPF view.

Table 500 Configure Route Summarization Within OSPF Domain.

Operation	Command
Configure route summarization within	abr-summary address mask mask area
OSPF domain.	area-id[ advertise notadvertise ]
Cancel route summary between areas	undo abr-summary address mask mask
	area area-id

By default, inter-area routes are not summarized.

It must be noted that a routing summary configuration is only valid on the ABR.

Creating and After the OSPF area division, all the areas may not be of equal size. One particular Configuring a Virtual area is unique and that is the backbone area with the area-id of 0.0.0.0. OSPF

Link route update between non-backbone areas is carried out through the backbone area. The OSPF protocol requires that all non-backbone areas be connected to backbone areas and at least one port on an ABR must be in the area 0.0.0.0. If there is no physical connection between an area and the backbone area 0.0.0.0, a virtual link must be created.

If a physical connection is not possible due to the limitation of the network topology, a virtual link can satisfy this requirement. Virtual link refers to a logical connection channel between two ABRs that is created through an area of non-backbone area internal routes. Both ends of the virtual link must be ABRs and both ends must be configured at the same time so that the virtual link can take effect. A virtual link is flagged with the ID of the opposite router. The area providing the non-backbone internal route for both ends of the virtual connection is called a transit area, whose area-id must also be specified.