I have exhausted all my local expertise as well as my own experimenting with this problem, so I'm at the proverbial dead end.
I have two DVR's for surveillance, and old Lorex and a brand new Zmodo 8 channel. Everything was working just fine on regular DSL service, remote viewing, login, etc. Only one DVR is on the network at a time. Actually, I thought the NIC card went bad in the Lorex, so I got a new Zmodo as a replacement. As soon as we added 30 meg VDSL, it was discovered that the 30 meg pipe dropped to less than 2 meg. Pull the DVR off of the network, and all is well again. I've tried home runs from the DVR straight to the modem (to eliminate the possibility of switch/router problems), but this gremlin continues to haunt me. At least the old Lorex would be highly intermittent about it, but the new Zmodo takes it down instantly and stays there.
One would think a NIC on a network device is a NIC.....no difference, but on a VDSL line, that apparently is not true. Any help would be deeply appreciated.