Hi, thanks for prompt reply. I'm using mine with the Virgin Media Superhub 3.0 and I could only get it to work with 378.53.I finally gave up on my AC87U (sold it). I replaced it with the AC88U. My new setup is as follows:
1) AC88U w/ 380.63_2 (main router/gateway to Internet)
2) AC68U w/ 380.63_2 (media bridge mode connected to AC88U on 5Ghz)
3) AC68U w/ 380.63_2 (repeater mode connected to AC88U on 5Ghz)
Everything working smoothly. So repeater mode on AC68U does work...it just depends on what router it's repeating from.