What is the max length for a fully (DNS) qualified hostname?

[vikrantl]

newton.mass.america.earth.com....
Is there any limit to te length of a fully qualified host name?

[Ranjith_5]

Hi Vikrant,

63 octets per label. 255 bytes per FQDN (254 bytes for the FQDN plus one byte for the terminating dot).

see table 3.7 in http://www.microsoft.com/resources/documentation/WindowsServ/2003/all/deployguide/en-us/Default.asp?url=/resources/documentation/WindowsServ/2003/all/deployguide/en-us/dnsbd_dns_rcvz.asp

That means 63 characters per label.

See this page paragraph 6.

http://www.tcpipguide.com/free/t_DNSNameNotationandMessageCompressionTechnique.htm#Figure_252

regards,
Syam

[vikrantl]

Thanks Syam for the info.

What would be the practical on site big big name lengths that anyone has come accross?

[Stuart Browne · Accepted solution]

I honestly don't think I've seen anything more than about 50 characters, usually in the middle of large network router families.

Longest I could find in some quick playing was 40:

dcr1-so-3-3-0.SanFranciscosfo.savvis.net

Bug I guess if you're talking internal departmentalized records, I guess they could stack a bit, something like:

....

sort of thing *shrug*. No limit to the amount of dots in the middle ;P

[vikrantl]

I see,
thanks for the info. everyone!