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DNS issues using Cisco isr4431 behind FWP

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Slussjc1
I have an isr4431 behind a fwp and I can ping and traceroute to public sites, but DNS isn't working on my test pc. The connect will flap between connected and not connected every 30 seconds or so. I have Google dns set as dns server on router sub int and manually set it on my PC connection, again trying to rule out fwp dns server as the issue. Network topology is from inside out: Pc>cat3850>isr4431>netgear unmanaged switch>FWP I've tried putting a port 53 rule to allow dns traffic. I've tried completely turning off monitoring. I can see port 53 in the ip nat translations on the isr4431, but the connection continues to flap.
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    Firewalla

    Is the FWP connecting to the modem? 

    If you connect another device to your netgear switch, does the DNS work?

    What function does the isr4431 provide in your network? does it create another subnet or it is in bridge mode?

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    Slussjc1

    The FWP is the gateway to my network providing connection to isp.

    I also have a netgear router connected to the switch with the dns set to the fwp dns address with no issues.

    The isr4431 simply provides me a test network for professional practice and hobby. It has its own subnets with dhcp and is not in bridge mode.

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    Firewalla

    Do you have any filtering going on with the isr? I can't think of anything else if your netgear works and isr doesn't ... 

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    Slussjc1

    No ACLs are setup on the isr except the one to identify the subnet IPs to be brought into the NAT process. But no ACLs restricting traffic.

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    DB

    Where the netgear router and your computer are connected to the ISR, switch them around and retest.

    Does the PC now work and the Netgear doesnt?

    Also look at the routing table on your PC.

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    Firewalla

    Another thing, double check your PC (if it is running bitdefender) or Cisco (has port scan protection). Firewalla has a feature that scan/map your LAN and that action at time may trigger things on these system. You can turn it off by tapping +, then "device port scan", turn it off

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