Background: I have a windows server 2012 install with AD, DNS and DHCP.
I also have a netopia router/modem providing my WAN access.
My router/modem is configured with DHCP off and connected to a 24 port switch. My WS2012 has static IP and uses the router/gateway as its default gateway for internet traffic and uses loopback for DNS. This WS2012 is also connected to same 24port switch.
The Problem:
My DNS server has forwarding enabled to my ISP's dns servers.
Here is the problem: All my workstations on the network are getting extremely slow internet access (.1-.2 Mbps). Connecting directly to the modem and setting static IP (and completely bypassing the WS2012) gets about 4-5 Mbps. The reason I think this is a DNS issue is because whenever I go into DNS manager and clear the Cache the internet on all machines runs at 4-5 Mbps for about 10-20 minutes and then slows to crawl again.
I have already checked my reverse lookup records and forward records and they seem to be in-tact.
This issue just arose about 1 week ago and this WS2012 has been in production for 6-7 months without a single hickup. No configuration changes have been made to this machine. Nobody has even logged into this machine (headless) since put into production besides a monthly reboot (from login screen via RDP).
PS. All internal traffic runs at full speed.