Routing
Dlink DRO-220i User Guide
33
OSPF
In the Link State algorithm, Nodes generate link state packets with costs of attached links
and distribute to other nodes using acknowledged flooding algorithm. Nodes individually
run Dijkstra’s shortest path algorithm.
Open Shortest Path First (OSPF) is one of the most common link State algorithms. OSPF
works by abstracting the collection of actual networks, routers and lines into a directed
graph in which each arc is assigned a cost. It then computes the shortest path based on the
weights of the arcs. When a router boots, it sends HELLO messages on all of its point-to-
point lines and multicasts them on LANs to the group consisting of all the other routers.
OSPF works by exchanging information between adjacent routers, which is not the same
as between neighboring routers. To avoid this situation one router is elected as the
designated router. It is said to be adjacent to all other routers, and exchanges information
them. Neighboring that are not adjacent do not exchange information with each other.
During normal operation, each router periodically floods LINK STATE UPDATE
messages to each of its adjacent routers. This message gives its state and provides the
costs used in the topological database. The flooding messages are acknowledged, to make
them reliable. Each message has a sequence number, so a router can see whether an
incoming LINK STATE UPDATE is older or newer than what it currently has.
DATABASE DESCRIPTION messages gives the sequence numbers of all the link state
entries currently held by the sender. Each partner can request link state information from
the other one using LINK STATE REQUEST messages. The net result of this algorithm
is that each pair of adjacent routers checks to see who has the most recent data, and new
information is spread throughout the area this way. All these messages are sent as raw IP
packets.
Select
Routing
→
Dynamic
to configure
OSPF Settings
as explained below.
OSPF Settings
Routing Protocol
Select
OSPF
to configure dynamic routing.
Router Id
Enter the Router ID of the OSPF Router. It should be in the form of IP
dotted decimal format
Redistribute
Static, Connected Routes and RIP routes can be redistributed into OSPF
table, so that these routes are also sent with the route updates.
OSPF Daemon
Select Start or Stop to activate or deactivate the OSPF daemon.
Interface Settings
Interface Name
Select the Interface Name, OSPF can be configured on that. Interface
WAN2 can be configured as a single 64kbps, single 128kbps or two
64kbps channels. In case of single channel, only B1 will be configurable by
the User. In case of two channels, both B1 and B2 can be configured.
Enable
Select Enable to activate OSPF on the corresponding interface.
Web UI
