OSPF Router Protocol

It is very useful to know some knowledge about OSPF router protocols. Many people may not know the commands commonly used in OSPF router protocols and the explanations of some terms. It does not matter. After reading this article, you will certainly have a lot of GAINS, I hope this article will teach you more things.

Advantages of the OSPF Router Protocol:

① Rapid response to network changes;

② Send triggered updates when the network changes;

③ Supports the VLSM variable-length subnet mask );

④ Convenient management.

⑤ Unlimited skip count;

⑥ Enable the integration of devices from multiple vendors ).

OSPF Router Protocol terminology:

Link: A link is a network or router interface specified to the network. When an interface is added to this OSPF interface, it is considered as a link by OSPF. This link or interface will have a status information assigned to it UP or DOWN, that is, activation or failure), and one or more IP addresses.

Vroid ID: vroididrid) is an IP address used to identify the vro. Cisco specifies the router ID by using the highest IP address in all configured loopback interfaces. If no loopback interface with an address is configured, OSPF selects the highest IP address among all activated physical interfaces as its RID.

Neighbor: A neighbor can be two or more routers. Each of these routers has an interface connected to a public network, such as two routers connected to a point-to-point serial link.

Adjacent: the relationship between the two OSPF router protocols. The two routers allow direct exchange of Route updates. The OSPF Router Protocol is very considerate about the shared route selection information. It does not share the route information directly with all its neighbors as it does.

HELLO protocol: OSPF Hello protocol can dynamically discover neighbors and maintain the relationship between neighbors. Hello data packets and link status announcement LSA) establishes and maintains the topological database. The address of the Hello packet is the multicast address 224.0.0.5.

Neighbor relational database neighbor table): the neighbor relational database is a list of OSPF router protocols. The Hello packets of these routers can be seen by each other. The neighbor relational database on each router manages various details, such as the router ID and status. Stores information about the neighbor router.

Topology database topology table): the topology database contains information from all the link status notification packets received from a region. The router uses the information from the topology database as the Dijkstra algorithm input and calculates the shortest path for each network.

Forward database route table): used to save the optimal route from the topology database to the target network.

Link Status notification LSA): A link status notification is an OSPF Packet that contains the link status and route information shared in the OSPF Router Protocol. There are multiple types of LSA data packets, which are detailed in CCNP. The OSPF Router Protocol will only exchange LSA data packets with the vro that establishes an adjacent relationship.

Specify a router DR): whenever the OSPF Router Protocol is connected to the same multi-channel access network, You must select a specified router. To ensure that the topology tables on all vrouters are synchronized, all vrouters in the shared network will be connected to the DR and BDR standby vrouters. For detailed analysis, follow the subsequent CCNP articles.

Specify the Standby Router BDR): The Standby Router is a standby DR on the multi-channel access link. BDR receives all route updates from the OSPF router-connected router, but does not send these LSA updates.

Anti-mask wildcard mask): The wildcard mask (or anti-mask) used by the router is used together with the source or target address to identify the matched address range, which is exactly the opposite of the subnet mask.

Decimal wildcard mask calculation method:

The subnet mask value is expressed in binary format, and the difference value is calculated using the broadcast address, and then the return value is decimal. That is, the formula is introduced: wildcard mask = 255-mask. 255-mask. 255-mask. 255-mask.