In the process of determining the best path, the routing algorithm needs to initialize and maintain the routing table. The routing information contained in the routing table varies according to the routing algorithm. Generally, the routing table includes such information as destination network address, related network nodes, satisfaction with a certain path, expected path information, etc.
Routers transmit a variety of information to maintain the routing table, and modifying routing messages is the most common one. The modified routing message is usually composed of all or part of the routing table. The router constructs a complete network topology detail by analyzing the latest messages from all other routers. Link state broadcast is a kind of route correction information.
Route
After the router is configured, it learns paths from other routers through routing protocols. These paths are called routes. The router keeps a routing table in RAM, which is a list of the best routes. Routers use this table to decide how to forward packets.
Routing
We use the command “show ip route” on the Cisco router[300-410] to observe the routing table. The routing table maps the network prefix to the outbound interface. For example, when the router receives a network segment with a destination of 2.3.3.0/24 from the interface, it will look for the prefix 2.3.3.0/24 in the table and then send it out from another interface. In the routing table of the above example, we can see that there are three routes in the direct network, which are marked with C in the routing table. As a router, if it forwards to other network segments, the router must include more routes.
The ways to add routes
There are two ways to add routes to the router: Static route – the administrator manually defines the route to the destination network or several networks. Dynamic route – Routers exchange routing information according to the rules defined by routing protocols, and independently select the best path. Administratively-defined routes are called static routes because they will remain unchanged until the network administrator manually intervenes.
Routes learned from other routers are called dynamic routes, because when neighboring routers update each other with new routing information, they may change automatically. Each method has basic advantages and disadvantages. Static routes occupy less router resources and require less equipment.
There is no bandwidth occupation, no need to generate routing update information, which can also make the network more secure, because dynamic routing protocols are often the most accessible link for intruders. In addition, static routing has more predictable types. The administrator can accurately control the routing of the router…
Compared with static route, dynamic routing protocols have strong adaptability and can automatically select the optimal path to the target network to transfer data. The maintenance workload is small. In addition, it can find the failed link in time and notify other routers of such changes. The only difference in router configuration between Cisco, Huawei, H3C, Ruijie and other manufacturers is that the configuration command is slightly different, and the principle is the same.
