Application of OSPF routing protocol in Enterprise network

Now the enterprise network is often used in the construction of OSPF, this agreement to do some elaboration.

OSPF is called Open Shortest Path priority protocol, and all device vendors support a protocol which belongs to link state routing protocol, which is suitable for large enterprise network.

OSPF has many advantages, 1. The trigger update route, as long as the network topology changes, will immediately trigger the update of the routing table. 2. Send some routes according to the link state. 3. Use group advertisement to send routing protocol. There are two available multicast IP addresses 224.0.0.5, 224.0.0.6. 5. The applicable network is large in size and has virtually no size limit of 6.metric cost. 7. Faster convergence speed, and will not cause routing loops 8. There are three tables: (1) The neighbor table by sending the Hello package with the Neighbor Exchange information (2) The link state database, also known as LSDB (3), lsdb the entire routing table (9) To support variable eldest subnet mask and subnet discontinuity according to the database. These advantages are not available in other low-end routing protocols. (10) Multiple equal-cost routes that support the same destination address.

The process of generating OSPF routing tables:

Each router sends the LSA (Data link State database) to other routers based on the link state, and then the routers in the network aggregate all the LSA received into a LSDB (link state database). Then each router uses SPF algorithm to calculate a shortest path by the tree-like structure, so that each node routing, resulting in routing table.

OSPF can be divided into single zone configurations and multiple zone configurations, and single zones are often applied to small networks.

Multi-area OSPF is the most used in the enterprise network, and the whole network can be regarded as composed of several self-made systems. In different areas of OSPF, area 0 is the backbone area, in the backbone area, in order to ensure packet forwarding speed, the number of routers is as small as possible, and as an area 0 router, the stability is very strong, the faster the better.

AREA1 is a standard area, and each standard area must be connected to a router with a backbone region (area 0) and is not directly connected to the standard area.

Stub areas are usually located at the boundary of the homemade system, also known as the distal region.

The complete stub area is also known as the complete distal region. In this area, there is no route to any other homemade system.

The OSPF model has different roles and names depending on where the router is located, and the router's port is assigned to multiple zones, so this router is called an ABR (area border router). ABR is the boundary route of backbone region. A router that connects to a homemade system is called a ASBR (homemade system boundary router). Because most of the routing protocols are different between the two, it is usually necessary to redistribute the route in order to realize the communication between autonomous zones and other networks.

about OSPF multi-zone configuration:

Equipment requirements: 6 routers, of which ROUTER2 has 4 serial interfaces.

Experimental purposes:

Among them, R1, R2, R3 and R4 operate the OSPF protocol in different regions;

R1 in Area 1 as a stub region, R4 in area 2 as a complete stub region.

R5, R6 in the self-made area to run RIP v1, to achieve a full network interoperability.

Learning a default route in RIP to communicate with OSPF;

Learn all the detailed routing tables in the area0 area of OSPF

Only one default path is learned in area 2 and the routing table for network devices in the region is communicated to all network devices across the network