Detailed analysis of DNS troubleshooting steps

In the face of more and more complex network applications, many networks will encounter one or more faults. Now, let's analyze the DNS troubleshooting process. This section describes the precautions, troubleshooting procedures, and detailed troubleshooting steps for configuring DNS in a typical DNS networking environment.

DNS troubleshooting: Typical Networking Environment

Typical DNS networking 1 is shown. DNS troubleshooting will be based on this network.

Figure 1 Typical DNS networking

In this networking, the router interface works with the DNS Client and the DNS Server to allow the router interface to access the host with the IP address 1.1.1.2/16 through the domain name paiwei.com, and configure the domain name suffix com and net.

DNS troubleshooting: configuration considerations

DNS troubleshooting: Fault Diagnosis Process

For the network shown in figure 1, after the configuration is complete, it is found that the correct IP address cannot be resolved on the router. Use the following fault diagnosis process, as shown in figure 2.

Figure 2 DNS fault diagnosis process

DNS troubleshooting: troubleshooting procedure

Procedure

1. Check whether the static domain name is correct

Run the command "display ip host" or "display ipv6 host" to check whether the domain name to be resolved exists in the static domain name table and whether the domain name and ip address match correctly.

◆ If the domain name exists but the ip address corresponding to the domain name is incorrect, run the command ip host or ipv6 host to make the domain name and ip address match correctly.

◆ If this domain name does not exist, perform step 2.

2. Check whether the dynamic domain name cache information has a domain name

Run the command display dns dynamic-host or display dns ipv6 dynamic-host to check whether the domain name to be resolved exists in the dynamic domain name table.

◆ If this domain name does not exist, perform step 3.

3. Check whether the IP address of the DNS server is correct.

Run the command display dns server to check whether the IP address of the DNS server configured on the DNS Client is correct.

◆ If the ip address of the configured DNS server is incorrect, run the command dns server ip-address or dns server ipv6 ipv6-address [interface-type interface-number] to reconfigure the ip address of the DNS server. If routeconfig still cannot be correctly resolved to the IP address, perform step 4.

◆ If the IP address of the configured DNS server is correct, perform step 4.

4. Check whether dynamic domain name resolution is enabled

In the system view, execute the command display current-configuration to check whether routers' dynamic domain name resolution function is enabled.

◆ If dynamic domain name resolution is not enabled, run the dns resolve command to enable dynamic domain name resolution. If routeconfig still cannot be correctly resolved to the IP address, perform Step 5.

◆ If dynamic domain name resolution is enabled, perform Step 5.

5. Check whether the domain name suffix is correct

Run the display dns domain command to check whether the domain name suffix is correct.