Dynamic routing! Dynamic routing! The principle and configuration of dynamic routing

1. Introduction to dynamic routing

1. Dynamic routing

Refers to the use of routing protocols by routers to learn about networks and update routing tables.

2. Routing protocol classification

3. Introduction to administrative distance

Administrative distance (AD) is used to determine the credibility of routing information received from adjacent routers. It is an integer from 0 to 255, where 0 means the highest credibility and 255 means that no data flow will use the corresponding route.

Default pipeline distance (Show ip protocols to view the AD value of dynamic routing)

4. Metrics

A metric is a value that a routing protocol assigns to the cost of routing a network to a remote network.

The metrics used in IP routing protocols are as follows:

5. Convergence

• Router convergence completed
• When all routing tables contain the same network information
• As the routers continue to exchange routing information
• Convergence ends when there is no information
• The network is not fully functioning when reaching the convergence money

6. Distance Vector-Routing Loops

(1) What is a routing loop?

A routing loop is a phenomenon in which a data packet is continuously transmitted between a series of routers but never reaches its intended destination network.

(2) Impact of routing loops

• Routers in the loop occupy link bandwidth to repeatedly send and receive traffic.
• The router's CPU is overwhelmed by the constant circulation of packets
• Affects network convergence
• Routing updates may be lost or not processed in a timely manner

(3) Anti-loop mechanism

• Define a maximum measure to prevent counting to infinity
• Inhibit Timer
• Split Horizon
• Route poisoning or poison reverse
• Trigger Update

2. Update of RIP routing information

1. RIP routing information updates are based on time period updates (update period is 30 seconds)

When the network topology connected to router A changes, router A updates its routing table and waits until the next sending cycle to announce the updated routing table. After receiving this update information, router B updates its own routing table

2. RIP configuration

Configuration commands:

 router rip

network Classified network (network10.0.0.0network tells the routing protocol RIP which classified networks to announce)

• version 2
• no auto-summary (turn off summary)

View the show ip route command

The experimental environment is as follows:

(1) Configure the IP address of router R2 interface and configure RIP routing

(2) Set up routers R1 and R3 in the same way

(3) View the routing table show ip route