5.3 Errors in DNS Configuration
The 10 most common errors in DNS configuration are as follows:
1. Every host in the Internet should have a domain name correctly established in the DNS. Some services check the existence of the name in the DNS and do not communicate with the host if this DNS name does not exist.
2. The domain name must not contain any other symbols than ASCII letters, digits, and a dash (not underscore!). A name should not consist of digits only. A name must not start or end with a dash. RFC 1033 permits the use of an underscore in a domain name; however, it is not defined as a standard and some implementations have problems with it, and it is therefore better to avoid its use.
3. Full domain names must end with a dot. A dot is not used at the end of an IP address.
4. The symbol
@in a mail address for an SOA record must be replaced by a dot.5. The right side of an NS record must include a canonical name; it must not include an IP address.
6. An A record and matching PTR record...
