Troubleshooting DNS Issues

In this article we will discuss Troubleshooting DNS Issues, will make brief discussion on Troubleshooting DNS Issues, In last article we discuss about Default Gateway Issues.

Domain Name Service (DNS) defines an automated service that matches names, such as www.cisco.com, with the IP address. While DNS resolution is not crucial to device communication, it is very important to the end user.

It is common for users to mistakenly relate the operation of an Internet link to the availability of the DNS service. User complaints such as “the network is down” or “the Internet is down” are often caused by an unreachable DNS server. While packet routing and all other network services are still operational, DNS failures often lead the user to the wrong conclusion. If a user types in a domain name such as www.cisco.com in a web browser and the DNS server is unreachable, the name will not be translated into an IP address and the website will not display.

DNS server addresses can be manually or automatically assigned. Network administrators are often responsible for manually assigning DNS server addresses on servers and other devices, while DHCP is used to automatically assign DNS server addresses to clients.

Although it is common for companies and organizations to manage their own DNS servers, any reachable DNS server can be used to resolve names. Small office and home office (SOHO) users often rely on the DNS server maintained by their ISP for name resolution. ISP-maintained DNS servers are assigned to SOHO customers via DHCP. For example, Google maintains a public DNS server that can be used by anyone and it is very useful for testing. The IPv4 address of Google’s public DNS server is 8.8.8.8 and 2001:4860:4860::8888 for its IPv6 DNS address.

Use the ipconfig /all, to verify which DNS server is in use by the Windows computer.

The nslookup command is another useful DNS troubleshooting tool for PCs. With nslookup a user can manually place DNS queries and analyze the DNS response.

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