Network troubleshooting method based on Ping Command

Document directory

• 1. Ping 127.0.0.1
• 2. Ping 192.168.1.10 [if this is the IP address of the Local Machine, use ipconfig to view the result]
• 3. Ping 192.168.1.38 [assume this is the IP address of a host in the same network segment in the LAN]
• 4. Ping 192.168.1.254 [assume this is the IP address of the gateway]
• 5. Ping 202.114.38.62 [A reachable remote IP address, confirm that the host is on and its Firewall does not prohibit Ping]
• 6. Ping localhost
• 7. Ping www.baidu.com [select any common domain name]

If you fail to access the network, it is a very likely problem in your life. Once you encounter a problem, you have to wait for the network management center to solve it. This is a little troublesome and time-consuming. Sometimes the problem may be very simple. We only need some simple methods to solve the problem on our own. At this time, why not? What I want to share with you is how to solve some simple network faults through the ping command.

When detecting network faults using the ping command, you must follow a fixedOrderEach step has its own value. If the failure in each step corresponds to some possible faults, ping the link after resolving the fault, but the link may still fail to be connected to the network, so proceed to check whether there are other faults.

For the sake of grounding, this article assumes that you are using the Windows 7 operating system and is based on this description.

 

1. Ping 127.0.0.1

Description: This step is used to test whether the installation or running of the TCP/IP protocol stack of the Local Operating System is faulty.

Function: In this step, if you can ping but still cannot access the network, it has nothing to do with the system TCP/IP protocol stack. You should continue to check whether the local Nic is running properly;

Faults and Countermeasures: If this step fails, you should re-run or re-install the TCP/IP protocol stack.

Supplement:

• The IP address of the 127 CIDR Block is a reserved IP Address used for network software testing to communicate with local processes. When the destination IP address is in the 127 CIDR Block, the packet is returned to itself when it leaves the network layer. The network adapter is not involved in the whole process and no network transmission is performed, therefore, the IP address of CIDR Block 127 is also called the return address and return address.
• In fact, 127.0.0.1 to 127.255.255.254 are both delivery addresses, but generally 127.0.0.1 is used. In the ping command application, one or more ". "0" is omitted. For example, it is completely available to rewrite the "Ping 127.0.0.1" command to "Ping 127.1. If one or more ". 0 "is not followed by the last part of the decimal number, but is in another position, then this". "0" cannot be omitted. For example, "Ping 202.0.96.1" cannot be written as "Ping 202.96.1 ". This is because "Ping 202.96.1" returns "202.96.0.1" instead of "202.0.96.1.

 

2. Ping 192.168.1.10 [if this is the IP address of the Local Machine, use ipconfig to view the result]

Description: This step is used to test whether the local network adapter (also known as the NIC) is running properly,

Purpose:In this step, if you can ping but still cannot access the network, it has nothing to do with the local Nic. You should continue to check whether there is a problem with the local network device.

Fault: If this step fails, possible problems include:

• "Local Connection" is disabled in the Local Operating System (or other connections you are using );
• There is a problem with the direct connection network cable;
• The direct connection switch is not started;
• The local network configuration is incorrect;
• Local NIC Driver problems;
• Nic itself or installation problems.

Countermeasure: You can try the following methods accordingly,

• When the NIC has an indicator, check whether the indicator is on. If the indicator light is off, perform the following steps to exit as long as the NIC light is on ],
  • Open "network and sharing center" and find "Change adapter Settings" in the upper left corner to ensure that the "connection" currently used is not disabled by the operating system;
  • Replace an intact network cable;
  • Change an available switch interface;
  • Re-plug/re-weld network card; [Use with Caution !]
  • Change the NIC. [Use with Caution !]

After the above steps are completed, the indicator light should be on. [Exercise caution when using the last two steps of the last five steps .] Ping the IP address of the Local Machine and continue to the next step;

• Disconnect the network cable, reconnect, and immediately ping the IP address of the local machine. If this is done, this indicates that an IP address conflict occurs at the beginning (that is, another computer in the LAN is configured with the same IP address as you), then you can configure an unused IP address, otherwise, go to the next step;
• Update the NIC Driver and ping the IP address of the local machine. This step is fine.

Supplement:

• It must be noted that the NIC indicator light only indicates that the interface for direct connection between the local upper-level network device and the local Nic is normal, it does not indicate that the network device is working normally (that is, it may not have a normal switch/route forwarding function). This is also the problem to be solved in the following two steps.

 

3. Ping 192.168.1.38 [assume this is the IP address of a host in the same network segment in the LAN]

Description: This step is used to test the connectivity within the LAN. [This step is generally used only when the LAN topology is complex. If there is only one network cable between the local machine and the egress router, skip this step]

Function: In this step, if you can ping but still cannot access the network, it is not a problem with LAN lines and network devices. You should continue to check whether the gateway is running normally.

Fault: If this step fails, possible problems include:

• The local subnet mask is incorrectly configured;
• The network cable in the LAN is broken;
• Network devices connected to the local machine are shut down due to a fault;
• The network device interface directly connected to the local machine is damaged.

Countermeasure: You can try the following methods accordingly,

• Check whether the configured subnet mask is consistent with that specified by the network management center;
• Check which level begins to cause a problem and change the corresponding line and switch.

Supplement:

• When the network topology is complex (one line is connected to multiple switches), it is generally refined by classification;
• If Ping is performed only once, the destination IP address and gateway must be directly connected to the same vswitch.

 

4. Ping 192.168.1.254 [assume this is the IP address of the gateway]

Description: This step is used to test whether the router is started.

Function: In this step, if you can ping but still cannot access the network, it is not a problem that the egress router is shut down or the direct connection interface is damaged. You should continue to check whether the router's routing function is normal.

Fault: If this step fails, possible problems include:

• There is a problem with the network cable connecting directly to the gateway;
• The switch interface of the direct connection gateway is faulty;
• The router interface used as the gateway in this section is damaged;
• The egress router is shut down due to a fault.

Countermeasure: You can try the following methods accordingly,

• Test the connectivity of the network cable of the direct connection gateway. If there is a problem, replace it with a new one;
• Connect a vswitch interface to the gateway;
• Replace a vro interface and reconfigure it as the gateway of this network segment;
• Restart/Replace the egress router.

 

5. Ping 202.114.38.62 [A reachable remote IP address, confirm that the host is on and its Firewall does not prohibit Ping]

Description: This step is used to test whether the route forwarding function of the egress router is available.

Function: In this step, if you can ping but still cannot access the network, it is not the cause of the failure of the egress router route forwarding function. Check whether domain name resolution can be completed normally.

Fault: If this step fails, it indicates that the route forwarding function of the egress router has some obstacles, possibly because the internal software is damaged.

Countermeasure: Restart/replace vro

Supplement: A remote IP address suitable for this step can be collected at ordinary times. Note/note several common Server IP addresses are helpful.

 

6. Ping localhost

Description: This step is used to test whether the local hosts file is available.

Function: If you can ping this step, the local WINS service is normal. If the DNS Service of the ISP (Network Service Provider) is faulty, You can temporarily use the local WINS service instead.

Fault: If this step fails, it indicates that there is a problem with the hosts file.

Countermeasure: You can find and modify the hosts file in the X: \ windows \ system32 \ drivers \ etc [X is a system disk] Directory.

Supplement: Localhost is the default entry in the hosts file, pointing to 127.0.0.1. Under normal circumstances, each host can convert localhost to 127.0.0.1

 

7. Ping www.baidu.com [select any common domain name]

Description: This step is used to test whether the ISP's DNS service is available.

Function: If Ping is enabled in this step, the DNS Service of the ISP can be used normally.

Fault: If this step fails, the possible problems include:

• An incorrect DNS server address is configured on the local machine;
• The configured DNS server fails and is unavailable;
• The server corresponding to the selected domain name has a fault;

Countermeasure: You can try the following methods accordingly,

• Make sure that the configured DNS server is consistent with that provided by the ISP and there are no low-level errors;
• Try several frequently-used domain names, such as www.sohu.com and www.sina.com;
• Use a backup DNS server, such as 8.8.8.8 provided by Google;
• Write some common domain names into the hosts file to solve the urgent need.