Sophos RED15 not booting properly, System light is on, Router is blinking - somtimes it comes on and then no internet connection is possible and the red is restarting.(i can see the lease on the DHCP server but RED ist never pingable) DHCP in the network is working properly all necessarcy ports are opened. i also tried with a second factory sealed RED 15 same behaviour. RED 10 on same network work just fine. I used a RED15 a week ago on same internet connection without problems
Is UDP/3410 allowed? There's been a couple of threads recently where an ISP level IPS was filtering/blocking the traffic. You should be able to check by using something like UDPing http://kb.netop.com/article.php?id=396 or NPing.
This is most likely the issue. If you need, you can open a case with Sophos Support to assist.
SCE, SCA v9.3