Very Simple DNS Tips and Tricks on Red Hat Linux 5.x

by Nathan Wallace (April 28, 1999)

Introduction

When my first web site went live I was so excited that I checked the statistics continually. I couldn't even wait for the compiled stats from wusage. I was checking the raw log files.

Of course, since there were almost no visitors my log file looked like this:

    /wusage/access-log
    /wusage/access-log
    /wusage/access-log
    /index.html
    /logox4.gif
    /wusage/access-log
    /wusage/access-log
    /wusage/access-log

While trying to track down the origins of the IP addresses that were appearing in my log file (before DNS resolution was turned on) I discovered the tools in this document. Some of them I used to check progress as the synop.com domain was changing between hosting companies.

Calculating the Hostname from the IP Address

To work out the hostname associated with an IP address use the ipcalc function.

    ipcalc --hostname 216.71.34.45
    HOSTNAME=synop.com

Getting Information about a Domain from Name Servers

The name servers on the internet cache information about domain names. This cache is updated periodically from the root DNS servers which are currently controlled by internic. If you make a change to your domain, such as changing hosting companies, then the name servers for the domain will usually change. This change takes time (approx 1-2 days) to filter to all computers on the internet.

To get the information about a domain from your default name server use:

    dnsquery synop.com

;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 6793
;; flags: qr rd ra; Ques: 1, Ans: 3, Auth: 2, Addit: 2
;; QUESTIONS:
;;	synop.com, type = ANY, class = IN

;; ANSWERS:
synop.com.	4228	IN	NS	ns.propagation.net.
synop.com.	4228	IN	NS	ns2.propagation.net.
synop.com.	3613	IN	A	216.71.34.45

;; AUTHORITY RECORDS:
synop.com.	4228	IN	NS	ns.propagation.net.
synop.com.	4228	IN	NS	ns2.propagation.net.

;; ADDITIONAL RECORDS:
ns.propagation.net.	171941	IN	A	216.71.32.31
ns2.propagation.net.	171941	IN	A	216.71.94.4

You can also ask other name servers on the internet for their records for a domain:

    dnsquery -n ns.internic.net synop.com

;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 44074
;; flags: qr rd; Ques: 1, Ans: 2, Auth: 2, Addit: 2
;; QUESTIONS:
;;	synop.com, type = ANY, class = IN

;; ANSWERS:
synop.com.	172800	IN	NS	NS.CIHOST.COM.
synop.com.	172800	IN	NS	NS2.CIHOST.COM.

;; AUTHORITY RECORDS:
synop.com.	172800	IN	NS	NS.CIHOST.COM.
synop.com.	172800	IN	NS	NS2.CIHOST.COM.

;; ADDITIONAL RECORDS:
NS.CIHOST.COM.	172800	IN	A	216.71.93.147
NS2.CIHOST.COM.	172800	IN	A	216.71.94.5