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1. The concept of dynamic routing
Dynamic routing means that the router can automatically establish its own routing table, and can adjust it in a timely manner according to changes in the actual situation.
1. The characteristics of dynamic routing
1) Reduce management tasks
2) Occupy network bandwidth
2. Overview of dynamic routing protocols
Router protocol: The language used to exchange information between routers.
1) Metrics: hops, bandwidth, load, delay, reliability, and cost.
Routers will use metrics to determine the optimal routing path.
2) Convergence
makes all routing tables complete The process of reaching a consistent state
3) The relationship between static routing and dynamic routing Static routing and dynamic routing in the
network complement each other
3. Classification of dynamic routing protocols
According to the algorithm classification performed by routing
1) Distance vector routing protocol (legend)
selects routing based on the number of routers passing from the source network to the destination network (for example: RIP, Cisco proprietary protocol IGRP)
2) Link state routing protocol (passing Letter)
Comprehensively consider the conditions of each path from the source network to the target network, and select the route (such as OSPF, IS-IS)
Two, RIP routing protocol
The RIP protocol is a distance vector routing protocol.
1. Basic concepts of RIP
The RIP protocol is mainly used for routing information transmission in small networks. It exchanges routing information (messages of the entire routing table) with neighbors through UDP packets, specifically port 520, and the update cycle is 30S; RIP protocol provides hop count as a metric to measure routing Distance, hop count is the number of routers that a packet must pass through to reach the destination. The maximum number of hops supported by RIP is 15, 16 is unreachable.
Keywords: regular update, neighbors, broadcast update, full routing table update
2. The formation of the routing table
1) The router learns the direct route.
2) When the update period of 30s is reached, the router sends its routing table to the neighbor.
3) After the second update period of 30s, the router sends the routing table to the neighbor again
3. RIP protocol anti-ring mechanism
Route poisoning
When the router finds that the route link is changed or down, it will poison the route, marking it as 16 hops, unreachable
Split
horizon Split horizon can prevent the occurrence of routing loops.
Routing information is learned from an interface and no longer sent back from this interface. At the same time, it can also reduce the link bandwidth resources occupied by routing update information.
4. The difference between RIPV1 and RIPV2
| RIP V1 | RIP V2 |
|---|---|
| Classful routing protocol (without mask when declaring information) | Classless routing protocol (declared information with mask) |
| Broadcast update (255.255.255.255) | Multicast update (224.0.0.9) |
| Does not support VLSM (VLSM is subnetting) | Support VLSM |
| Automatic route summarization, cannot be turned off | Automatic summary can be turned off, and can be manually summarized |
| Discontinuous subnets are not supported | Support for discontinuous subnets |
5. Configuration
1) Configure port IP address
2) Configure RIP protocol
[R1]rip 1
Start RIP, 1 is the name, and must be configured globally
[R1-rip-1]version 2
Start version 2, (default is 1)
[R1-rip- 1] undo summary
closes automatic route aggregation (that is, all routing table information is classified according to IP address)
[R1-rip-1] network 10.0.0.0
announces the network segment, V2 will carry the mask multicast update (224.0.0.9), V1 does not carry the mask broadcast update (255.255.255.255)
[R1-rip-1]network 192.168.10.0 The
following figure is the routing table of R1
