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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 */
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After reading this,…, and pouring through technet I couldn't find a definitive answer. – John Jul 15 '10 at 17:17
up vote 4 down vote accepted

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)

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The DNS suffix list is not the same as the DNS server list, and I don't think there's any reason to expect the maximum number of servers in the two lists to be the same. – coneslayer Jul 15 '10 at 18:36
@coneslayer: Quite right. I found more pertinent information that I edited above. – harrymc Jul 15 '10 at 19:56
Thanks a lot for your answer. Maybe I'll play around a bit and try to find out if something strange happens. :-) – qbi Jul 15 '10 at 23:05

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.

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