protectionpax.blogg.se - Ospfv2 with router on a stick

Init state – a router has received a Hello message from the other OSFP routerĢ. OSPF neighbor statesīefore establishing a neighbor relationship, OSPF routers need to go through several state changes. A dead timer is four times the value of the hello interval, so if a routers on an Ethernet network doesn’t receive at least one Hello packet from an OSFP neighbor for 40 seconds, the routers declares that neighbor to be down. The following fields in the Hello packets must be the same on both routers in order for routers to become neighbors:īy default, OSPF sends hello packets every 10 second on an Ethernet network (Hello interval).

using the highest IP address of the router’s physical interfaces. using the highest IP address of the router’s loopback interfaces.ģ. using the router-id command under the OSPF process.Ģ. A router ID is determined by using one of the following:ġ. Each OSPF router is assigned a router ID. In the example above, you can see that the router-id of R2 is 2.2.2.2. You can verify that the neighbor relationship has indeed been established by typing the show ip ospf neighbors command. After OSFP is enabled both routers send Hellos to each other to establish a neighbor relationship. Routers R1 and R2 are directly connected. The process is explained in the following figure: Hello packets are sent to the multicast IP address of 224.0.0.5.

OSPF neighbors are dynamically discovered by sending Hello packets out each OSPF-enabled interface on a router. OSPF routers need to establish a neighbor relationship before exchanging routing updates.

Topology table – stores the topology structure of a network.

Neighbor table – stores information about OSPF neighbors.

Because each router knows the entire topology of a network, the chance for a routing loop to occur is minimal.Įach OSPF router stores routing and topology information in three tables: Each OSFP router then runs SFP algorithm to calculate the best routes and adds those to the routing table. Instead, they exchange information about network topology. Because OSPF is a link state routing protocol, neighbors don’t exchange routing tables. Routers running OSPF have to establish neighbor relationships before exchanging routes.

uses multicast addresses 224.0.0.5 and 224.0.0.6 for routing updates.

the administrative distance of OSPF routes is, by default, 110.

uses only one parameter as the metric – the interface cost.

supports VLSM, CIDR, manual route summarization, equal cost load balancing.

Here are the most important features of OSPF: OSPF will run on most routers that doesn’t necessarily have to be Cisco routers (unlike EIGRP which can be run only on Cisco routers). Because it is an open standard, it is implemented by a variety of network vendors. OSPF (Open Shortest Path First) is a link state routing protocol.