working on that right now. Have 2 modems running to figure this issue out. Didnt know how to telnet and neither did suddenlink support. Going to try it now.
No luck on the telnet tried suddenlink google and dslr host.com and a few others. I have a IP address 3 dns address and everything looks line on my end and suddenlinks. But still says unable to connect to dsn servers contact your ISP.
Who's 3 DNS IP's are assigned in your router? You don't by chance have MAC spoofing enabled do you (on the DPC3825)? Also, have you taken a look at the modems error logs for any outstanding oddities? Sorry for all the questions I just find this behavior rather bizarre.
I've also read somewhere that having "Block IP Flood Detection" enabled in the DPC3825's configuration can cause random issues as well.