Explore three common dynamic routing protocols

The dynamic routing protocol is also an important part of the routing protocol. Many people may not know the detailed knowledge of RIP, OSPF, and VPN in the dynamic routing protocol, after reading this article, you must have gained a lot. I hope this article will teach you more things. We have already briefly introduced three types of Dynamic Routing Protocol algorithms: Distance Vector Algorithm, link state algorithm, and balanced hybrid algorithm. Let's take a look at the types of these algorithms today: RIP, OSPF, and VPN. And they are all internal gateway protocol IGP). That is to say, they all run in an autonomous system. What is an autonomous system? Let's take a look at it:

Autonomous System: a network set that uses the same routing rules. Generally, it is an ISP or a large administrative organization. When you hear this term, you will feel a little vague and abstract. We will provide a detailed introduction in the CCNP course. We rarely use protocols between Autonomous Systems in the CCNA part, the protocols used are basically those in autonomous systems. Therefore, dynamic routing protocols can be used to connect different autonomous systems based on whether they are running in an automatic system:

The CCNA Department focuses on the internal gateway protocol, so we should first open the RIP. RIP is a typical distance vector Dynamic Routing protocol. Its full name is Routing information protocol ). It uses the gateway through which data packets are transmitted as the unit of distance. The maximum hop count is 15 hops, which cannot be reached after 15 hops. You can see from this number, RIP is an old-level dynamic routing protocol, which is limited by 15 hops, so it is used less and less now. It is only suitable for some small networks with a small number of routers. The advantage of network evaluation is to rely on the number of hops, but this number does not necessarily represent the optimal path.

If PC1 is expected to reach PC2, it must pass through Router3 according to the RIP Protocol, and then be transferred to Router4 to reach PC2, because in this case, it only needs to go through two hops compared to Router3, the CIDR block of pc2. The minimum number of hops. However, the bandwidth of this line is 19.2 Kbps, while the other line has many Jumpers, but it is a T1 line with large bandwidth and low latency. It will certainly be better than the first one. However, RIP calculates the optimal path based on the number of hops, so it chooses the first path. As a result, we also feel that RIP is so stupid that it is not used much now! When the RIP Protocol is enabled, the RIP sends a broadcast packet from the RIP interface. Port 520/UDP is used here. The content of a broadcast packet mainly refers to the request information. It listens to the request information and response information from other routers. When a neighbor receives the request information, it sends a response to the router. After the RIP is started successfully, the average duration is 30 seconds. Note that the average duration is 30 seconds, not 30 seconds. The response message is also called the update package. This update package contains the complete route table of the router. Here, there should also be parameters such as invalid route values and route refresh time. This part should be the content of CCNP. Here is a brief introduction. For details, refer to the NP section.

If the 40 CIDR blocks connected to Router3 are disconnected. In contrast to Router2, if you do not get a route message about 40 CIDR blocks within 180 seconds, it will be considered invalid, but it is only invalid, set the route entry of 40 CIDR blocks on Router2 to the holddown state. The default time is 180 seconds. If Router2 receives a feasible route entry of 40 CIDR blocks within 180 seconds, it will stop timing and change the original route entry about 40 CIDR blocks to a available route entry. If it passes 240 seconds, I still don't get confirmation about the 40 CIDR block. I think this CIDR block is "Dead quietly", so I will delete it from the routing table.

RIP is divided into RIP1 and RIP2. The difference is that RIP1 is a dynamic routing protocol, that is, all update packages do not contain subnet masks and do not support VLSM, therefore, all devices in the network must use the same subnet mask. Otherwise, an error occurs. RIP2 is a classless dynamic routing protocol that uses the subnet mask; the second difference is that RIP1 uses a broadcast package when sending an update package, while RIP2 uses multicast 224.0.0.9, which saves part of the network bandwidth compared with rip1. The third is that RIP2 supports plaintext or MD5 verification. It requires that the two routers verify the route table while synchronizing the route table. Only when the two routers pass the verification can the routing be synchronized. This improves the security.

The configuration of RIP is relatively simple. Next we will end the discussion of RIP in experiment. Here we will do two experiments, one with RIP1 and the other with RIP2. In fact, their configurations are similar. Let's look at rip1.