Ospf - D-Link xStack Reference Manual

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xStack DGS-3620 Series Layer 3 Managed Stackable Gigabit Switch Web UI Reference Guide
Destination IPv4
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Destination IPv6
Address
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OSPF

The Open Shortest Path First (OSPF) routing protocol uses a link-state algorithm to determine routes to network
destinations. A "link" is an interface on a router and the "state" is a description of that interface and its relationship
to neighboring routers. The state contains information such as the IP address, subnet mask, type of network the
interface is attached to, other routers attached to the network, etc. The collection of link-states is then collected in a
link-state database that is maintained by routers running OSPF.
OSPF specifies how routers will communicate to maintain their link-state database and defines several concepts
about the topology of networks that use OSPF.
To limit the extent of link-state update traffic between routers, OSPF defines the concept of Area. All routers within
an area share the exact same link-state database, and a change to this database once one router triggers an
update to the link-state database of all other routers in that area. Routers that have interfaces connected to more
than one area are called Border Routers and take the responsibility of distributing routing information between
areas.
One area is defined as Area 0 or the Backbone. This area is central to the rest of the network in that all other areas
have a connection (through a router) to the backbone. Only routers have connections to the backbone and OSPF
is structured such that routing information changes in other areas will be introduced into the backbone, and then
propagated to the rest of the network.
When constructing a network to use OSPF, it is generally advisable to begin with the backbone (area 0) and work
outward
Link-State Algorithm
An OSPF router uses a link-state algorithm to build a shortest path tree to all destinations known to the router. The
following is a simplified description of the algorithm's steps:
When OSPF is started, or when a change in the routing information changes, the router generates a link-state
advertisement. This advertisement is a specially formatted packet that contains information about all the link-states
on the router.
This link-state advertisement is flooded to all routers in the area. Each router that receives the link-state
advertisement will store the advertisement and then forward a copy to other routers.
When the link-state database of each router is updated, the individual routers will calculate a Shortest Path
Tree to all destinations
destination address, associated cost, and the address of the next hop to reach each destination.
Once the link-state databases are updated, Shortest Path Trees calculated, and the IP routing tables written if
there are no subsequent changes in the OSPF network (such as a network link going down) there is very little
OSPF traffic.
Click the radio button and enter the destination IPv4 address of the GRE tunnel
interface. It is used as the destination address for packets in the tunnel. The address
type that will be used depends on the Delivery Protocol. The address type used at
both the source and destination must be consistent, otherwise, the GRE tunnel will
not work.
Click the radio button and enter the destination IPv6 address of the GRE tunnel
interface. It is used as the destination address for packets in the tunnel. The address
type that will be used depends on the Delivery Protocol. The address type used at
both the source and destination must be consistent, otherwise, the GRE tunnel will
not work.
with the individual router as the root. The IP routing table will then be made up of the
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