1. What is RIP. WHAT)
RIP: routing information Protocol. Simply putDynamic Routing ProtocolAlthough it was almost never used, its appearance had a cross-era significance.
2. when talking about the Static Routing Protocol, it was said that when there are many routers to be configured and there are many route entries, dynamic routing is used for automatic configuration, it is time-saving and time-saving. You may need to manually relay the static route for one morning. It may take less than one minute.
Automatically learn. Of course, what's more important is what Static Routing cannot do:
It also automatically maintains the network.. If a vro In the topology becomes a machine, the static route does not know that it is a machine and will still send data packets to it. However, dynamic routing is different. Its neighbor will automatically detect that the router has crashed and then tell the other neighbor of the topology. Dynamically change the corresponding
Routing. Insert a paragraph here.
Vro: It is a real device. It is used to find its own IP address based on the destination IP address of the data packet.
Route tableAnd then throw the data packet from the corresponding interface.
Routing: It is the route. How do I go from A to B. Go to the address 100.10.1.20/24 and choose interface fastEthernet 0/1? Or the information serial 1/0?
Route table: ManyRoutingTogether, form the table that the router forwards data.
3. How does RIP work? First, RIP works at the application layer. It is based on UDP port 520. It now has two versions. We use the second version as the standard. Its working principle is actually quite simple. It keeps grouping outward every 30 seconds.
Broadcast version 1 is broadcast)A name is"
Response", This packet contains all the route entries it knows, as well as the route entry
Metric ValueValue generation ). However, its metric value measurement method is very simple, that is, "after a layer-3 device, its metric will automatically + 1 ".
What is the use of this metric value?It is used to select the optimal path. For example, when I arrive at 100.10.1.20/24, there are two routes available, one is going through two routers, and the other is going through three routers, if one metric is 2 and the other is 3, RIP automatically selects the route with metric 2 and sends data packets to it.
What if the metric values of the two routes are the same?This requires fairness. The two roads are sent in turn. First, one packet is sent in Route 1, then one packet is sent in Route 2, followed by Route 1, followed by Route 2, in this way, the loop goes down. Well, this is a professional term called"
Server Load balancer". However, this RIP rating metric standard,
There is a big drawbackIt does not care about the actual situation of the network. For example, the speed of a 1 Gbit/s optical fiber and a 1.544 Mbit/s T1 leased line is obviously different. However, RIP will regard them as the same. Such a Server Load balancer will cause a waste of optical fiber and a crush on leased lines. In the just-beginning stage of the Internet, everyone's network speed is almost the same, because it is very slow, so the calculation of the metric value by RIP is simple and convenient. However, after the development of the Internet, the speed of the network has been greatly improved. Such metric value calculation is no longer suitable for the current situation. Therefore, it is natural to be eliminated. Also, send a message every 30 seconds.
Response packet,The same neighbor sends a Response packet every 30 seconds. Therefore, RIP has four related timers. If the timer is not sent within 30 seconds, the neighbor may be abnormal. No, I will wait. If the Response packet is not received in 180 seconds, the neighbor may be abnormal. But I cannot assert it so easily, so I will give another one-minute opportunity, that is, I haven't received the neighbor's Response packet after 240 seconds. Okay,
This neighbor has crashed. Then
Multicast outside, tell other routers that the neighbors are finished, so don't send data packets to them. The detour should be done without bypassing, clear the route entries from your route table.. Create a new route table to form a new network topology. -- "What are the five anti-ring routing mechanisms ?" -- "1. horizontal segmentation; 2. Maximum 16 hops; 3. Route poisoning; 4. Toxicity reversal; 5. Inhibition timer. Report to Tian Jie. The answer is complete !"
