Not Available chars on DNS

[Fabrizio Alleva]

Hi, I want to know the list of the special chars for the hostname which are not available in DNS database.
I know that there are some chars like "_" which gives some problems with the resolutions of the name with a DNS.
"Non Authoritative Answer" is the answer of the nameserver when I try to resolve a name with the nslookup command. I know where is the problem and I need this list.
Thank you.

[John Bolene]

If you stick with letters and numbers and of course the period (.), you will be fine.
Most if not all of the special chars are just that, special.

[Herve BRANGIER · Accepted solution]

Hi,

DNS syntax is define in RFC 1035, you can find
it at : www.cis.ohio-state.edu/cgi-bin/rfc/rfc1035.html

You can use [a-z][A-Z][0-9] and "-" in domain
name. Dot is a reserved character and others
are forbidden.

See the grammar for a domain name below :

"The following syntax will result in fewer
problems with many applications that use
domain names (e.g., mail, TELNET)."

::= | " "

::= | "."

::= [ [ ] ]

::= |

::= | "-"

::= |

::= any one of the 52 alphabetic characters A through Z in
upper case and a through z in lower case
::= any one of the ten digits 0 through 9



HTH

Herve

[Jim Turner]

The last time I checked the RFC, allowable characters were letters, numbers, the dot (.) and the dash (-). Although mixed-case is allowed, it is recommended that you stick wtih lower-case letters. Also, keep hostnames at or less than 64 characters.

Cheers,
Jim

[Kenneth Platz]

Fabrizio,

A "non-authoritative answer" simply means that the DNS server that you are performing the query against is not authoritative for the domain you are querying against. If you wish to find an authoritative answer, do the following:

$ nslookup
Default Server: ns02.gwin.charter.com
Address: 209.186.12.3

> set type=ns
> foo.com
Server: ns02.gwin.charter.com
Address: 209.186.12.3

Non-authoritative answer:
foo.com nameserver = NS2.OKDIRECT.com
foo.com nameserver = NS.OKDIRECT.com

Authoritative answers can be found from:
NS2.OKDIRECT.com internet address = 209.54.94.4
NS.OKDIRECT.com internet address = 209.54.94.5
> server 209.54.94.5
Default Server: ns.okdirect.com
Address: 209.54.94.5

> set type=A
> foo.com
Server: ns.okdirect.com
Address: 209.54.94.5

Name: foo.com
Address: 209.54.94.99

>

I hope this helps.