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Question
Monday, June 13, 2016 6:26 PM
Hi,
How is the A records priority defined in a Windows DNS server?
I have servers with two or more IP addresses. They have A records for each IP address.
My local network is 192.168.40.0/21 and when I try to ping some of those servers it's messing my head up.
Server X has this IP addresses: 192.168.46.107, 192.168.69.170 and 192.168.102.170.
Server Y has this IP addresses: 192.168.46.65 and 192.168.69.65.
When I try to ping server Y, it returns the correct IP 192.168.46.65. When I ping server X it returns this IP: 192.168.69.170.
What is the priority here? I thought it was the record creation order. So I've deleted the 192.168.69.170 and 192.168.102.170 A records from the DNS servers, re-added them... and it still pings the 69.170 IP...
Is there a way to say to Windows: "This is my preferred IP address among all of them, use THIS one"?
All replies (4)
Monday, June 13, 2016 8:33 PM ✅Answered
Is there a way to say to Windows: "This is my preferred IP address among all of them, use THIS one"?
The real question here is, if you only wish the name be resolved to one of the addresses, why do you need to have A records for the other addresses in your DNS?
If you *really* needed to have multiple IPs on the same NIC but only one of them resolvable via DNS, you should turn off auto-registration on that NIC and create a static DNS record with the preferred address.
Evgenij Smirnov
msg services ag, Berlin -> http://www.msg-services.de
my personal blog (mostly German) -> http://it-pro-berlin.de
Windows Server User Group, Berlin -> http://www.winsvr-berlin.de
Mark Minasi Technical Forum, reloaded -> http://newforum.minasi.com
In theory, there is no difference between theory and practice. In practice, there is.
Tuesday, June 14, 2016 1:40 AM
Hi,
>>Is there a way to say to Windows: "This is my preferred IP address among all of them, use THIS one"?
There are two mechanism:Round Robin and Netmask Ordering.DNS Round Robin is a mechanism for choosing an IP address from the list returned by a DNS server so that all clients won’t get the same IP address every time. Netmask ordering is a mechanism for further optimizing which IP address is used by attempting to determine the closest result.
According your description,I think you need Netmask Ordering,by default,Round Robin and Netmask Ordering are both checked in DNS server properties Advanced tab.You could try to uncheck Round Robin,keep only Netmask Ordering.
And this link for your reference:
DNS Round Robin and Destination IP address selection
________________________________________
Best Regards,
Cartman
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Tuesday, June 14, 2016 11:38 AM
The real question here is, if you only wish the name be resolved to one of the addresses, why do you need to have A records for the other addresses in your DNS?
If you *really* needed to have multiple IPs on the same NIC but only one of them resolvable via DNS, you should turn off auto-registration on that NIC and create a static DNS record with the preferred address.
_______________________________________________________________________________
There are two mechanism:Round Robin and Netmask Ordering.DNS Round Robin is a mechanism for choosing an IP address from the list returned by a DNS server so that all clients won’t get the same IP address every time. Netmask ordering is a mechanism for further optimizing which IP address is used by attempting to determine the closest result.
Evgenij Smirnov and Cartman Shen,
Thanks for the replies.
The scenario is a little bit complex... We have other companies that access this resources using NAT for those different ranges 192.168.69.0/24 and 192.168.102.0/24. Talking with our Linux/Firewall guy yesterday and he will try to avoid our creation of those IP addresses using DNAT (or SNAT, don't remember correctly now). But today we need to have those IP addresses for the other networks, but for the local network we want an specific IP address to be resolved.
On one server I did that configuration to not register the NIC on DNS, but Y server is a Domain Controller and I don't like to keep messing with it.
About Round Robin and Netmask Ordering, our local network used to be only 192.168.40.0/21 and both were active and working. But now we are adding another local networks (separated by VLANs): 192.168.220.0/23 and others above it. So on my PC, when I try to to ping those machines, the DNS understands that I'm not in the local network anymore and does Round Robin with the other two addresses. Last week we have disabled those options, since it was not working the way we wanted anymore. That's why I was asking which priority is given on DNS records... There should be a reason why it picks one address only among others, right?
I was hoping that I was able to add more local network mask to DNS server, but it seems to not be possible...
Tuesday, June 14, 2016 11:52 AM
Hi,
multihomed domain controllers have never (as in : EVER) worked well. Apart from that, you can have as many IP addresses as you like but if you really only want one to be resolved via DNS, you have no choice than to disable autoregistration and create a static IP.
Alternatively, you could work with multiple NICs if that's possible and only enable autoregistration on the one the 'correct' IP is bound to.
Evgenij Smirnov
msg services ag, Berlin -> http://www.msg-services.de
my personal blog (mostly German) -> http://it-pro-berlin.de
Windows Server User Group, Berlin -> http://www.winsvr-berlin.de
Mark Minasi Technical Forum, reloaded -> http://newforum.minasi.com
In theory, there is no difference between theory and practice. In practice, there is.