RIP Protocol for the most basic Routing Protocol

The routing information protocol (RIP) is one of the earliest and most basic protocols in the routing protocol. Although its current use is gradually unable to meet our network construction needs, we still need to fully master this protocol as a learning basis. Like all protocols, the RIP Protocol is used to distribute router-related network information, the router needs to know what network can be reached and how far it is from these networks. The RIP Protocol is still widely used ｡

Many people cursing the RIP Protocol, saying that the aggregation speed is too slow, there is no scalability and security, because the RIP Protocol only supports plaintext authentication, this protocol is also affected by the Split-horizon protocol. These situations are true. However, this protocol is still very useful. We hope this article will explain these issues, helps you understand one of the most widely used internal gateway protocols ｡

There are two versions of the RIP Protocol: the first version (r1_1) and the second version (r1_2). r1_1 has very limited functions because it does not support CIDR (classless Inter-Domain Routing) address Resolution. This means that this Protocol is only a domain-like protocol. You cannot divide the 24-mask network into smaller units, r12001 also uses broadcast to send messages. This means that the host cannot ignore RIP broadcasts. Remember that each host in the broadcast domain will receive an interruption each time a broadcast is sent, this packet must be processed to determine whether it is a concern. r12002 uses Multicast technology. This technology will be introduced in subsequent lectures, you only need to know whether the host can ignore this multicast packet without processing this packet ｡

Remember, we once said that RIP is a distance vector protocol. The distance mentioned here refers to the number of hops in the RIP Protocol, vector refers to the destination. Other distance vector protocols may use other rules to measure each vector, for example, AS-PATH in the BGP protocol. The two versions of RIP Protocol send messages to UDP port 520 every 30 seconds. But what information does they send? If you guess it is "their route information", you have guessed it. RIP can send specific information about the network it can reach, and broadcast it as a default gateway (the destination is 0.0.0.0, And the metric value/metric is 1 )｡

R12002 data packets have their own headers, the same as many other protocols. Note that the RIP Protocol is based on the UDP protocol. Therefore, it is actually an application layer protocol. Each RIP packet contains a command, a version number, and a route domain. Then, a maximum of 25 route information (within one packet) is followed )｡

RIP packet instructions

A rip command can be a request or a response. When a host (either a Unix server or a router) is started for the first time, the host needs to obtain some routing information. At this time, a "request" command will be issued. A packet containing the request command will be broadcast to the network. "response" is another common RIP command. It is used to answer. one request, or, it is only a simple broadcast once every 30 seconds ｡

Version: the version number is one or two, indicating the RIP Protocol version of this packet ｡

Route domain: A route domain in the RIP Protocol is an identifier used to specify the route instance. More than one set of RIP instances can exist in the same network, you can specify an information that is only sent to a person in a specific domain ｡

Other parts of the RIP Packet

After the routing domain, the real RIP route information starts. A data packet can contain up to 25 route entries. Each route entry must contain the following information:

◆ Network Address: Identify the start point of the target subnet address ｡

◆ Subnet mask: Description