DNS

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Testing

I use DNSdoctor

CNAME versus A records

In general, avoid using CNAME records. Always use A records.

It is common to get A records and CNAME records mixed-up when learning DNS. A does not stand for alias; A stands for Address. It maps a name to an IP address. CNAME might sound like you are defining a canonical name, but it is the other way around. It maps an alias name to a canonical name. So really, the CNAME record is the type of record used to define an alias, but you don't use it even that way. If you want to have different names point to the same IP address you simply define multiple A records that map different names to the same address. So what kind of aliases to CNAME records define? They define pointers to hosts managed on different DNS servers. A CNAME record is like a link out of out of the current directory. If you don't need to link different DNS zones then don't worry about CNAME records. If a CNAME record appears for a host in a zone file then you must not have any other types of records for that host.

resolv.conf

I add some public nameservers to the end of my resolv.conf on my home machines. These are not the fastest or most reliable nameservers, but they keep my machine going if my ISP DNS goes down. I use OpenDNS and I also add 4.2.2.2 because it's easy to remember and it's open. PortForward maintains a list of public DNS servers.

On Ubuntu and Debian you may find that changes to resolv.conf disappear from time-to-time. This is because you are not supposed to manually edit the resolv.conf file anymore. See Resolv.conf for more information.

nameserver 208.67.222.222
nameserver 208.67.220.220
nameserver 4.2.2.1
nameserver 4.2.2.2
nameserver 4.2.2.3
nameserver 4.2.2.4
nameserver 4.2.2.5
nameserver 4.2.2.6
nameserver 198.6.1.1
nameserver 199.166.24.253
nameserver 199.166.27.253
nameserver 199.166.28.10
nameserver 199.166.29.3
nameserver 199.166.31.3
nameserver 195.117.6.25
nameserver 204.57.55.100