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2 Different Subnets Windows not Acccessing DNS

Quick question. I have 2 subnets both in the LAN zone one at 192.168.0.0\24 and 192.168.2.0\24. The first is on Port1 and the second is a WiFi network. Each has its own DHCP server with a DNS setting of 192.168.0.1 which is the Sophos XG. I have LAN to LAN rule for communication between the two networks. I setup a static host in the DNS server called ITSM1908 with ip address of 192.168.0.138. A Win 10 device on 192.168.2.5 can ping/http/https and even goto a specific address 192.168.0.29 by using ip address to devices on the 192.168.0.0/24 subnet. Alll have internet access just fine. The one problem comes in when the Win 10 machine trys to query the DNS at 192.168.0.1. If it queries any internet based address it comes back fine, but when I query for the ITSM1908 i get an error of DNS records ..... AAA and AAAA+ is not valid. When I query from the Win 10 device on 192.168.0.0 subnet it work fine and returns ITSM1908 with 192.168.0.138. I have preferred !Pv4 over IPv6 in DNS. Anyone know why this occurs?

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0 LuCar Toni over 4 years ago

Do you use the XG as a DNS request route?

There is some feature in windows, which adds a domain to a hostname all the time.

https://serverfault.com/questions/74067/windows-appending-domain-suffix-to-all-lookups

Maybe your client is doing the same?

So your domain is test.com, your hostname, you want to lookup is ITSM1908 (without anything). And Windows tries to reach automatically ITSM1908.test.com, while this domain is not reachable.

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0 LuCar Toni over 4 years ago

Do you use the XG as a DNS request route?

There is some feature in windows, which adds a domain to a hostname all the time.

https://serverfault.com/questions/74067/windows-appending-domain-suffix-to-all-lookups

Maybe your client is doing the same?

So your domain is test.com, your hostname, you want to lookup is ITSM1908 (without anything). And Windows tries to reach automatically ITSM1908.test.com, while this domain is not reachable.

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0 LocalAg02 over 4 years ago in reply to LuCar Toni

No request route.

The Win 10 machine on 192.168.1.0/24 can get request non-authoritative. Just not DNS static host record.

I will take a look at the link.

Thanks for replying. One more clue is I can put it in the Win 10 machine host file and it works as well.

Driving me insane.
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0 LuCar Toni over 4 years ago in reply to LocalAg02

You can verify this issue by "dumping" the DNS Traffic on Xg.

Simply place a tcpdump -ni any port 53

Or finetune this command. https://www.netmeister.org/blog/dns-tcpdump.html

If you see a request like my suggestion, windows is causing this.

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0 LocalAg02 over 4 years ago in reply to LuCar Toni

Intresting link. I had not seen nslookup with the set debug=true flag. I might try that and see what i get.
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0 LocalAg02 over 4 years ago in reply to LocalAg02

Well just found out the customer IT bridged the two interfaces together and it works fine now. Win 10 machine works when on the same subnet as DNS. I wish I had a little more time to test and see where the issue was.
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