RIP (Routing Information Protocol) Analysis 01

Differences between Static Routing and dynamic routing:

Static Routing: simple configuration and low device overhead Large Network workload, complicated troubleshooting, poor scalability Dynamic Routing: Strong scalability, easy to meet various needs, suitable for large Network Dynamic Routing Protocol classification: DV: the route is advertised in the vector distance-distance Metric, Direction-Where Next hop). The distance here is determined by the measurement. Each vro maintains a vector table that lists the best distance to each target and the lines used. Routers constantly update their internal tables by exchanging information between neighbors. Features: 1. Regular updates   2. Update the entire route table 3. Route Selection Based on rumors 4. Route timer 5. horizontal segmentation 6. Count to infinity 7. Trigger update 8. Suppression Timer 9. asynchronous LS update: The Link State routing selection Protocol, also known as the shortest path priority protocol, is based on Edsger Dijkstra's shortest path priority SPF algorithm. Advantages: 1. Create a topology 2. Fast Convergence 3. event-driven Update 4. Hierarchical Design of the RIP route protocol: RIP (route information Protocol) it is a standard for exchanging routing selection information between the gateway and the host. RIP is an early and widely used Internal Gateway Protocol (IGP). It is applicable to small similar networks and is a typical distance-vector Protocol. For more information, see RFC1058 and RFC1723. RIP is mainly designed to work with similar technologies and networks of moderate sizes. As a result, RIP is suitable for simple Campus Networks and area networks, but not complex networks, with little change in speed. RIP Protocol features: IGP, DV protocol based on UDP, port 520

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The complete update of the route table sent to the neighbor periodically only supports a maximum of 16 messages with an AD of 120 RIP: requests and responses. The former is used to request an update message, the latter is used to carry an update request to the neighbor (update ). At the beginning of a router running RIP, Each router interface broadcast (r12001) that initiates the RIP Protocol generates a packet with a request message, and then starts to listen continuously for requests or response messages from other routers. The router that receives the request message will send a response message containing all its route tables as a reply.

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After an interface is declared to the RIP process, a request message is sent immediately. The request message contains a AFI (address identifier) with 0 Metric as 16, which indicates all the routes of the request. After receiving the request message, the router returns a unicast reply message.

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In addition to the AFI format of the first package at the beginning of RIP creation, it is used to request routing. The reply message can be a response to the request, or an active update is used in special cases:

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If a vro has no interfaces to participate in the RIP Protocol except for the shared link, no reply message is sent (even if the request message is received) it does not take the initiative to perform periodic updates, because there is no route in the routing table that needs to be sent to the peer end. The same for V1V2If R1 only advertises the link connecting itself and R2. R1 will not send any other RIP packets except the first request packet to request the route. Two situations in which the RIP Router receives the Response Message: 1. if the received route entries are all new, the router adds the new route along with the advertised router address (source ip) of these routes to its route table. What is the next hop contained in volume 1? Most of them are differences in early IOS versions. The message does include the next hop, Which is 0.0.0.0 and should be the source ip address. Add it to the route table as the next hop. 2. if the received route entry already exists, only a few hops can replace the original route into the route table. RIP Timer: Update: Send messages from all interfaces that start RIP at a fixed time, it contains all its own routes (except those restricted by horizontal segmentation rules ). the reason for this time difference between 25.5 S and 30 S is that all routers take a random value in this period of time. RIP uses asynchronous updates. synchronous updates are prone to collision, a large number of repeated routes, and inefficient bandwidth utilization.

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Invalid, the route is marked as 16 hops. Holddown: when the number of hops received by a route entry is greater than the number of hops in the route table for 180 S, refresh: After the timer expires, clear the invalid route. Timers basicUpdateInvalidHolddownFlushThe default timer result is flush = invalid + holddown. If you change the timer, follow the principle below when flush timer is no greater than invalid timer for 10 seconds, 10 s after invalid timer expires, flush database. When flush timer exceeds invalid timer for more than 10 seconds, press flush timer.That is to say, flush takes at least 10 seconds after invalid.Different IOS versions may be different. 12.2 is 20 S, and 12.3 is 10 S.20 40 60 30At this time, 50th seconds flush20 40 60 70At this time, 70th seconds flush

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