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03.01.2008 at 04:21AM PST, ID: 23206031

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7.2

Can't resolve DNS after changing subnet mask

Zones: TCP/IP, Windows 2003 Server, Domain Name Service (DNS)

Tags: Microsoft, Server, 2003, Subnet Mask

We have a class C network 192.65.144.0/24. I am changing our internal network subnet mask from 255.255.255.0 to 255.255.254.0 to enable us to create a new DHCP scope with double the amount of IP's we currently have hence the network range would be 192.65.144.0-192.65.145.254.

We have 2 DNS server internally. They both have an IP in the 192.65.144.x range. When I change the subnet mask on these to 255.255.254.0 and go to a client on the new 192.65.145.x range I am able to sucessfully query one of the DNS servers however the other is unreachable. As it also runs exchange I am unable to connect exchange clients. Clients in the 192.65.145.x range can ping the DNS/Exchange server however they cannot resolve DNS queries from it. If I go to the DNS/Exchange server I can ping all clients on the 192.65.145.x range.

I have flushed the DNS cache on client & server. I have checked DNS is listening on the correct interface. I have restarted DNS on the server & I have restarted the server however I am still unable to query it from the 192.65.145.x.

I am pretty sure my proposed new subnet mask is valid as I am having no issues with my other DNS server. It is also on the 192.65.144.x range and clients on the 192.65.145.x range are able to query it sucessfully.

It appears that DNS is not applying the new subnet mask to the listening interface so won't communicate with clients on the 192.65.145.x range.

Any suggestions would be apprecaited.

Thanks,

Barry

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Question Stats

Zone: Networking

Question Asked By: maitteam

Solution Provided By: ryansoto

Participating Experts: 2

Solution Grade: B

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