QUESTION :
What is the maximum of nameservers one can enter in Windows? Are there differences in different versions? Linux has a maximum of three, which is set in /usr/include/resolv.h:
# define MAXNS 3 /* max # name servers we'll track */
ANSWER :
In this puzzle of Windows limits there isn’t much published information.
One just has to guess from what little information is known.
For example, Microsoft’s Configuring DNS client settings says :
When DNS clients are configured
dynamically using a DHCP server, it is
possible to have a larger list of
provided DNS servers. To provide an IP
address list of DNS servers to your
DHCP clients, enable option code 6 on
the configured options types provided
by your DHCP server. For Windows
Server 2003 DHCP servers, you can
configure a list of up to 25 DNS
servers for each client with this
option.
From this we can infer that MS considers 25 DNS servers to be “larger” than the default limit. Under normal conditions the limit would apparently be lower.
From Is there any limit for ” Append DNS Suffix” ?
I have too many domains in my org and
have added these domain in the DNS
Suffix list. Issue I am facing is, it
works perfect for the hosts in the
higher order DNS domain ( top 5), but
if I try to search ( nslookup) any
host in the lower order domain ( below
5) it fails. Also, if we move the
lower order domain in top 5 DNS
Suffix, it works.
Although it has been rightly remarked that this number has no direct relation to the number of DNS servers, it seems that the person who designed this interface liked multiples of five.
As a side-note, if you are interested in AD, then Active Directory limits says :
maximum number of DNS servers in an
AD-integrated zone (without manually
adding the details): 850 (Windows
2000), 1300 (Windows 2003)
I know that the advanced TCP/IP settings shown elsewhere with capability of many DNS server addresses has been a standard component of every Microsoft Windows DNS client going back to Windows 95 and Windows NT 4, though a DLL or method for entering them may have varied. It may go back even further, but I didn’t have to maintain a Windows IP network with older versions.
I also know that the first three hosts listed are used, because when our ISP’s two hosts were unavailable, the third host that was maintained by another company was used instead.