InternetPeriscope lets you look up the following types of DNS records:
- A Records. Given a domain name, InternetPeriscope can tell you the IP Address associated with that domain name, by looking up it's A Record.
- PTR Records. Given an IP Address, InternetPeriscope can tell you the domain name associated with that IP Address, by looking up it's PTR Record.
- NS Records. Given a Second Level Domain Name (SLD), InternetPeriscope can tell you which name servers are authoritative for that domain, by looking up the domain's NS Record. Note: Second Level Domain Names (SLDs) are domain names that have one period in them. For example, microsoft.com and cnn.com are SLDs. www.microsoft.com and www.cnn.com are NOT SLDs, because they both have two periods in them.
NS records will tell you which name servers the DNS administrator configured as authoritative for the zone. However, DNS administrators do sometimes make mistakes. To find out which Nameservers NetworkSolutions believes to be authoritative for the zone, use the Whois Tool.
- CNAME records are alias records. For example, www.microsoft.com is really any alias for www.microsoft.akadns.net. InternetPeriscope enables you to look up CNAME Records.
- MX Records are called "Mail Exchange" Records. They determine where the email for a domain should go. For example, if you sent email to cnn.com, your email would be routed to the machine named atlmail1.turner.com (or the machine named atlmail3.turner.com). InternetPeriscope enables you to determine which machines receive email for a domain.
- SOA Records are called "Start of Authority" Records. They tell you
- The Primary Nameserver of the domain. When a DNS makes changes to a domain's zone file, they usually perform the changes on this name server. The "secondary" name servers later receive the zone's changes from the primary nameserver.
- The email address of the person responsible for this domain.
- The Serial number of the zone. Every time the administrator changes a record in the domain's zone file, she increases this number. A secondary nameserver can use this number to determine if the primary nameserver has an updated zone file. If so, the secondary nameserver can request the new zone file from the primary nameserver.
- The refresh interval, in seconds. This is how often the secondary nameservers check with the primary nameserver to see if any changes have been made to the domain's zone file.
- The retry interval, in seconds. If a secondary nameserver is unable to contact the primary nameserver (perhaps it has crashed, or the connection between them is saturated), then it will retry the connection after this many seconds.
- The Expire interval, in seconds. If a secondary nameserver is unable to contact the primary nameserver for this many seconds, then it will "expire" the zone. That is, it will no longer answer questions about this domain.
- The Minimum TTL (time to live), in seconds. When you type in a URL like http://www.microsoft.com, your computer asks its DNS server for the IP address for www.microsoft.com. (This DNS server is probably located at your ISP). This DNS server then asks Microsoft's DNS server for the IP address of www.microsoft.com. Microsoft's DNS server returns an answer to your DNS server, which then caches this result for TTL seconds. By caching this record, it reduces the load on Microsoft's DNS server, and allows your web browser to more quickly connect to the website, as it doesn't have to spend a lot of time looking up the IP address.