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One way to test a DNS server is with the dig command. Once you configure a local DNS server as a slave or a caching name server, or any other kind of DNS server, you can use the dig command to test it. You can even test the DNS servers associated with your isp. We'll just examine a few basic options for the dig command. The format is: dig "atsign"server where server is the ip address of the DNS server in question, name is the domain name in question and type is the DNS record. For example, A is the authoritative DNS record, MX stands for mail exchanger, normally associated with the mail server. If no DNS server is specified, the dig command refers to the resolve or configuration file, etc dash resolv dot conf, and uses one of it's DNS servers. For example, if I want to identify VTCs email services, I'd run the dig vtc dot conf MX command. Note how it identifies the fully qualified domain name of the VTC e-mail server. If you just want to find the ip address to VTC servers, drop the MX. I get the authoritative ip address for VTC dot com. Just for yucks, let's run the dig command by itself. Gosh. Those are the root DNS servers for the Internet, and these are sort of the ultimate forwarders as they're supposed to know the DNS servers with authority for every domain name on the Internet. Let's try a reverse lookup. Reverse lookups are possible with the dash xswitch, and a reverse lookup associates a domain name with an ip address, so we use dig dash x and put in an ip address. Let's look up ip address 63 dot 161 dot 169 dot 137 and see what we get. Gosh, that's the ip address for the White House.
| Course: | Red Hat Certified Engineer |
| Author: | Michael Jang |
| SKU: | 33845 |
| ISBN: | 1-934743-47-X |
| Release Date: | 2008-01-18 |
| Duration: | 6.5 hrs / 94 lessons |
| Captions: | No |
| Compatibility: |
Vista/XP/2000, OS X, Linux QuickTime 7, Flash 8 |