How to use Ping & IP Config to check DNS

Ping is a very basic utility to troubleshoot DNS. It is only able to lookup A and PTR records. Nslookup and digger should be used for any advanced DNS query. On the other hand most users are very familiar and comfortable with the utility and, therefore, it is extremely easy to learn. Ping is also widely available in all operating systems.

Ping: A Record Look-Up A records map names to IP addresses. This is the default behavior when using ping.

Ping nightmare-066kgi.blogspot.com

In this example the ping utility performs two tasks. It first performs a DNS query to lookup the IP address corresponding to echofloor.com. Then, it then pings successfully the resolved 64.233.181.191 IP address.

It is also possible to resolve a name address into an IP address successfully but then fail the ping connectivity test.

Ping www.repair.com

Finally the A Record look-up may fail all together.

Ping IReallyDoNotExist.com

Ping: PTR Record (Reverse DNS) Look-Up

PTR records resolve an IP address to a name address. This process is also known as reverse DNS lookup. This can be done with ping by using the –a flag.

Ping -a 64.233.181.191

The reverse DNS of this IP address resolves back to nightmare-066kgi.blogspot.com. The reverse PTR record matching the forward lookup may be important to ensure web delivery.

Ipconfig: DNS Cache Display

Windows will cache DNS information as it is looked up. This process is done to speed up repeated identical queries. DNS responses from a DNS server include a “Time to Live” in seconds that is used to age out the entry from the DNS cache.

The ipconfig /displaydns command displays the contents of the DNS client resolver cache, which includes both entries preloaded from the local Hosts file and any recently obtained resource records for name queries resolved by the computer. The DNS Client service uses this information to resolve frequently queried names quickly, before querying its configured DNS servers.

The result here shows three DNS entries. The nightmare-066kgi.blogspot.com entry shows an IP address of 64.233.181.191. The time to live is 231

Ipconfig: DNS Flushing
Entries in the dns cache can be manually flushed using ipconfig. The “ipconfig /flushdns“ command flushes and resets the contents of the DNS client resolver cache. During DNS troubleshooting, you can use this procedure to discard negative cache entries from the cache, as well as any other entries that have been added dynamically. Flushing may also be necessary when DNS entries have been updated but the PC still holds the old DNS information in its cache.
The DNS flush is run successfully in the example below. Note that localhost entry always populates the DNS cache.
Ipconfig /flushdns 6

Ipconfig: DNS Register

The ipconfig /registerdns command instructs the network host to register its hostname and IP dynamically to the local DNS servers. Command initiates manual dynamic registration for the DNS names and IP addresses that are configured at a computer. You can use this parameter to troubleshoot a failed DNS name registration or resolve a dynamic update problem between a client and the DNS server without rebooting the client computer. The DNS settings in the advanced properties of the TCP/IP protocol determine which names are registered in DNS.

Note that this features mainly works with the Windows DNS Server.