I recently fixed an incompatibility between a Netgear router and a Comcast modem. My question is in regards to DNS forwarding. Did the protocol for DNS forwarding change? Or did Comcast recently change the way their business modems handle DNS forwards from internal networks?
The network in question is using a Netgear FVS model router bridged to a Comcast SMC business gateway.
The Netgear also handles DHCP on the LAN. For a year or more the Netgear ran "DNS Proxy" for its local DHCP clients. In other words, the router handed-out its own address for DNS.
It worked for months. In the last few days, somewhere between the Netgear and the SMC I found that DNS forwarding was dying and not recovering.
I applied a minor firmware version upgrade to the Netgear with no change in behavior. Comcast told me that their device had a good status with no pending updates. I still couldn't count on DNS proxy (aka forwarding).
The Netgear actually has a DHCP log, but not a DNS log. (These devices offer emailed logging, which didn't produce enough details for me in the past).
I kiled the DNS Proxy and everything works. Fortunately, there are few local resources on the LAN, and they can all be addressed by IP address instead of name resolution. The DNS Proxy isn't essential.
Summary: Now the Netgear provides DHCP clients with the public DNS server 18.104.22.168 and everything works.
Question: Why did DNS Proxy fail after many months of service?