8.1.2 Region Area

Use regional benefits:

* The router only needs to have the same link state database as the other routers in its region, and it is not necessary to share the same link state database with all routers in the entire OSPF area, so the indentation of the link state database reduces the consumption of the router's memory

* Reduced link state database means less LSA processing and lower CPU consumption by routers

* Because the link state database only needs to be maintained within one region, a large number of LSA flooding spreads are limited to one region

Zones are identified by a 32-bit area ID

Presentation mode:

Decimal digit or dotted decimal

Area0 and area0.0.0.0 are the same.

3 Regional-related traffic

Intra-domain traffic Intra-area traffic

Traffic made up of packets exchanged between routers in a single domain

Inter-domain traffic Inter-area traffic

The amount of traffic that is exchanged between routers in different zones

External traffic external traffic

Traffic that consists of packets exchanged between routers in an OSPF domain and routers in other routing domains

Zone 0 is the region number reserved for the backbone area

The backbone domain's task is to summarize the network topology of each zone to all other regions, so all inter-domain traffic must pass through the backbone domain, and non-backbone domains cannot exchange packets directly

1. Router type

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Internal router Internal Router

Routers that all interfaces belong to the same zone

Zone Border Router Area Border Router ABR

A router that connects one or more zones to a backbone area, which acts as a router gateway for inter-domain traffic

The ABR has at least one interface that belongs to the backbone area and must maintain a different link state database for each area connected to it.

Backbone Router Backbone Router

At least one interface is a router connected to the backbone area, meaning that the ABR can also be a backbone router

Autonomous system border Router autonomous system boundary Router ASBR

Traffic outside the OSPF domain enters the gateway router for the OSPF domain

2. Segmented area

A situation in which a part of an area is isolated from another due to a link failure

3. Virtual link

Links to backbone areas through a non-backbone area

Role:

(1) Connecting an area to the backbone domain through a non-backbone area

(2) A portion of a part of the backbone area connected to a segmented area through a non-backbone region

Virtual link Configuration rules:

* Virtual link must be configured between two ABR

* The area where the virtual link is configured must have all the router selection information, which is also known as the transfer area

* Delivery area cannot be a peripheral area

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8.1.2 Region Area