For vdsl users can not comment because this fixed faceplate is limiting the choices (all through to me is suspicious with draytek products) ...

but for adsl, i have a belkin (expensive) filter and the with the STD firmware was getting 2-3 disconnections daily
with the vectoring firmware the modem was rebooting each 1-3 min as soon i connect the cable back of the unit
i have change to a cheap splitter looking like this (not the same made but the same design - there are no cables to the splitter needs to use our own)
https://encrypted-tbn3.gstatic.com/images?q=tbn:ANd9GcQbEkpP3_dGsV7QSEPBk7C4H4Yb_WnsLGu4iEytsSKh1pNcl7-9
everything works perfect
The belkin was causing disconnection and made the unit to reboot for a reason

i am not saying everyone has the same issue but the ones having disconnections take out the cable from the socket like what i did ... if there is not reboots is the filter ...it may helps

i will report this to the support if is a help to the engineers and i have the syslog & wireshark capture if they want it

@saxtonma:
Thanks for the update. I don't have stability issues on ADSL 2+ with either 4.7.1 or 3.7.3, so long as UPnP is turned off.
Turn UPnP on, and you get reboots all the time.
I have seen problems with the WiFi on 4.7.1 though, such that for some devices, traffic get lost for about 20 seconds every 3 minutes or so.

@babis3g
It's not the filter, it's UPnP.
In fact, the filter filters interference from the telephone, and is supposed to leave the DSL socket untouched. Thus, plugging your modem into the filtered socket should be as good as plugging it into the test socket. In any case, a filter will only make a difference if you actually have a telephone connected to the line (which I don't).
Also not sure what vectoring has to do with ADSL. Vectoring is specific to VDSL, and will only be deployed to lines over 2km in length in the UK.
The ADSL equivalent is Annex L, and that has been a mature technology for a very long time now.

tobythetenor wrote:
@babis3g
It's not the filter, it's UPnP.
In fact, the filter filters interference from the telephone, and is supposed to leave the DSL socket untouched. Thus, plugging your modem into the filtered socket should be as good as plugging it into the test socket. In any case, a filter will only make a difference if you actually have a telephone connected to the line (which I don't).
Also not sure what vectoring has to do with ADSL. Vectoring is specific to VDSL, and will only be deployed to lines over 2km in length in the UK.
The ADSL equivalent is Annex L, and that has been a mature technology for a very long time now.

I did not mean there is not any issue with upnp, i just mean for some users that using adsl line it could be a case with the filter (like in my case) if they are using phone at the same time, so by plugging direct the modem in the phone socket like you or change filter or use of just a splitter may helps if there is another issue other than the upnp
I have inform the support in Taiwan and will investigate

I installed a 2860n for a customer last week, using Zen fibre through (PPPoE) on WAN2 and backup ADSL through WAN1.
This device is managing 5 x AP-900 access points too. Also the device is supporting a VoIP system using SIP trunks.

We found that after a day of it working absolutely fine that the router started to reboot every minute or two. We had to go out and replace it with a 2830n until we can get the problem resolved. We are using the latest firmware version (3.7.4.1)

This was installed in a cabinet which has 2 new lines installed by BT and the ADSL connection is using a filter and cable which was used on the previous connection for a few years without incident. I think i will be returning this and replacing with 2925

Just want to add that I'm another with the continuous rebooting of a 2860n with 3.7.4.1 firmware. And, surprise, surprise it started when Plex Media Server was locally installed. I was just about to give up on the Draytek and send back for a refund when I read this thread.
So will switch off uPNP and see what happens and then uninstall Plex (as not urgent) if that fails.

Good to read that Draytek are aware and there is a new firmware in the works.

I understand that it is resolved in beta f/w 3.7.5_test_r41111 which presumably you can request from UK support.