D-Link DES-3326S - Switch - Stackable Uživatelská příručka stáhnout pdf (Strana 136)

DES-3326S Layer 3 Fast Ethernet Switch User’s Guide

136 Switch Management and Operating Concepts

backbone through a router. OSPF allows routing information

to be distributed by forwarding it into area 0, from which the

information can be forwarded to all other areas (and all other

routers) on the network.

In situations where an area is required, but is not possible to

provide a physical connection to the backbone, a virtual link

can be configured.

Virtual Links

Virtual links accomplish two purposes:

1. Linking an area that does not have a physical

connection to the backbone.

2. Patching the backbone in case there is a

discontinuity in area 0.

Areas Not Physically Connected to Area 0

All areas of an OSPF network should have a physical

connection to the backbone, but is some cases it is not possible

to physically connect a remote area to the backbone. In these

cases, a virtual link is configured to connect the remote area to

the backbone. A virtual path is a logical path between two

border routers that have a common area, with one border

router connected to the backbone.

Partitioning the Backbone

OSPF also allows virtual links to be configured to connect the

parts of the backbone that are discontinuous. This is the

equivalent to linking different area 0s together using a logical

path between each area 0. Virtual links can also be added for

redundancy to protect against a router failure. A virtual link is

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D-Link DES-3326S - Switch - Stackable Uživatelská příručka Strana 136