Computer Network Experiment 3

1. Purpose of the experiment

1. Understand how routers work
2. Learn to use VNL's network device configuration and simulation platform to add routers, hosts and switches
3. Master the configuration of static routing and default routing, and independently set the IP address of the network segment
4. Master the two representation methods of IP subnet mask
5. Familiar with and use the interface of the router, learn to set up four routers on the simulation platform to realize the connectivity test of the host

 

2. Experimental environment

Computer, VNL.exe (Huawei's network device configuration and simulation platform)

 

3. Relevant principles and knowledge points

1. Basic structure of routing table
   A typical routing table instance is as follows
   
   Destination IP: Indicates the IP address of an identifiable target on the current router.
   Destination Mask: Indicates the mask of an identifiable target
   on the current router. Next Hop: The entry of the next directly connected router.
   Protocol: Indicates the routing protocol adopted, which is usually regarded as the type of the current routing item
2. IP subnet mask
   is a 32-bit IP subnet mask, which is characterized by consecutive 1s starting from the high bit, followed by consecutive 0s, and it has two representation methods.
   (1) Traditional representation, such as 255.255.255.0;
   (2) IP prefix, such as 192.168.1.3/24, indicating that the first 24 bits of the IP address are network bits

 

4. Experimental content

Experimental task 1: Design an IP network consisting of four routers under the emulator

1. Draw a network topology diagram
2. Divide IP network segments and assign network segment IDs to router interfaces and hosts
3. On each router, set static routing or default routing
4. Finally complete the connectivity test to ensure that the entire network is interoperable

Design idea
1. Prepare to use four routers, two switches and two hosts for connectivity when designing the topology diagram, and complete the test.
2. In order to distinguish the IPs of each network segment, the network segments are designed in order from 5.5.5.0 to 9.9.9.0.
3. For the convenience of the next hop, we arrange the routers in order.

Key details: When setting static routes, you need to set the subsequent IP addresses from the first one, and the number of routes set by subsequent routers will decrease in turn.

 

5. Experimental steps

Experimental task one

An IP network composed of four routers
1. Network topology diagram

2. IP planning
There are five network segments, and the IP distribution of network nodes is as follows

net1:
5.5.5.0/24 1-254 0-255
C1:5.5.5.1
Router1:e0:5.5.5.2
 
net2 : 6.6.6.0/24 Router1:e1:
6.6.6.1 Router2:e0:6.6.6.2 net3: 7.7. 7.0/24 Router1:e1:7.7.7.1 Router2:e0:7.7.7.2 net4: 8.8.8.0/24 Router1: e1:8.8.8.1 Router2:e0:8.8.8.2 net5 9.9.9.0/24 Router1:e1:9.9. 9.1 C2:9.9.9.2 (a lazy method, design the network segment as a sequential field, but it is easy to operate)


 




 




 

3. Host ip


4. Router routing table

(other pictures omitted)

4. Connectivity test
Click "T->" on the software, first click host C1, then click C2, observe whether the purple point can go from C1 to C2,
click "T->" on the software, first click host C2, then click C1 , observe whether the purple point can go from C2 to C1

 

6. Experimental results and analysis

Experimental Task 1 Results

The result is as shown below

Analysis:
According to the figure, the network addresses are divided in order, from 5.5.5.0 to 9.9.9.0, and the network planning is also from host C1 5.5.5.1 to host C2 9.9.9.2.
When setting a static route, the next hop of Router1 is the IP of Router2/E0, and the destination address includes the IP addresses of Router3, Router4, and the host; the next hop of Router2 is Router3/E0, and the destination address includes the IP address of Router4 and the host C2 ; The next hop of Router3 is Router4/E0, and the destination address contains the IP address of host C2.
Then conduct a connection test, find a path, and the connection test is successful. The opposite is also true for configuration from right to left. As can be seen from the figure, the test is successful, which proves that the configured network can communicate with each other.

network segment name	Network segment IP	communication node	communication node IP
Net1	5.5.5.0	C1	5.5.5.1
Net1	5.5.5.0	Router1:E0	5.5.5.2
Net2	6.6.6.0	Router1:E1	6.6.6.1
Net2	6.6.6.0	Router2:E0	6.6.6.2
Net3	7.7.7.0	Router2:E1	7.7.7.1
Net3	7.7.7.0	Router3:E0	7.7.7.2
Net4	8.8.8.0	Router3:E1	8.8.8.1
Net4	8.8.8.0	Router4:E0	8.8.8.2
Net5	9.9.9.0	Router4:E1	9.9.9.1
Net5	9.9.9.0	C2	9.9.9.2

Note: When setting static routing, you can not only set static routing between two routers, but also need to set static routing of other routers behind a router, including the IP address of the host

 

7. Experimental summary

1. This experiment environment is based on the Huawei 3com network equipment configuration and networking experiment simulation platform - VNL.exe. You need to click "T->", then click the start point and end point of the test network, and observe whether the purple dot can be connected to the end point to judge.
2. The focus of this experiment is on the division and planning of IP network segments. During the experiment in class, I failed to understand how the network segments are divided and when adding static routes, I mistakenly thought that the target network was the planned IP network segment. Stuck on Router3. Ask the classmates to know that the target network has to write the port of the router we want to connect to, and the next hop is to write the port we want to connect to the current router, and the port to be connected to all routers after the target network configuration on one router, otherwise It will not be able to connect to the router behind.
3. When connecting in the reverse configuration, after the routing table configuration in the four routers is completed, the connectivity test is performed, but it is found that the network Router4 we configured cannot be connected when the network is from E1 to E0, and finally it is found that the default gateway of the host C2 and Router4 The IP address of /E1 does not match, and it can be connected after modification.
4. Summary: Through this experiment, I have mastered the basic configuration of the router, know the operation process of VNL.exe, and can add four routers to realize the connectivity test between hosts. I designed the IP subnet division and network planning by myself, and at the same time learned about the network connection fault location method, that is, use the "T->" operation to click on the machine side to be tested. If there is no connection, narrow the scope until the test has a connection , the position of the open circuit can be determined.