Figure 26-2 Ospf Network Example - ZyXEL Communications Dimension ES-4024 User Manual

Dimension ES-4024 Ethernet Switch
26.1.2 How OSPF Works
Layer 3 devices exchange routing information to build synchronized link state database within the same AS or area.
They do this by exchanging Hello messages to confirm which neighbor (layer 3) devices exist and then they
exchange database descriptions (DDs) to create the link state database. The link state database in constantly updated
through LSAs (Link State Advertisements).
The link state database contains records of router IDs, their associated links and path costs. Each device can then
use the link state database and Dijkstra algorithm to compute the least cost paths to network destinations.
26.1.3 Interfaces and Virtual Links
An OSPF interface is a link between a layer 3 device and an OSPF network. An interface has state information, an
IP address and subnet mask associated with it. When you configure an OSPF interface, you first set an interface to
transmit OSPF traffic and add the interface to an area.
You can configure a virtual link to establish/maintain connectivity between a non-backbone area and the backbone.
The virtual ink must be configured on both layer 3 devices in the non-backbone area and the backbone.
26.1.4 Configuring OSPF
To configure OSPF on the ES, do the following tasks
•
Enable OSPF
•
Create OSPF areas
•
Create and associate interface(s) to an area
•
Create virtual links to maintain backbone connectivity.
26-2

Figure 26-2 OSPF Network Example

OSPF