I have vigor 2860n+
before upgrade:






and i updated firmware

using below file....

Firmware Information
Current Version 3.8.9.3_BT <<<<<<<<<< i use this firmware..

from https://www.draytek.co.uk/support/downloads/vigor-2860/send/344-vigor-2860/1442-v2860-3893-bt

Release Notes
Release Date 13/09/2018
Support Language English
Supported Models Vigor 2860
Vigor 2860n
Vigor 2860Vn
Vigor 2860n-Plus
Vigor 2860Vn-Plus
Vigor 2860ac
Vigor 2860Vac
Vigor 2860L
Vigor 2860Ln


now its rebooting... pls help me.... before upgrade its working fine...

wrong firmware?

What does the router now report it has installed ?

It's quite a jump version wise. The 3.8.9.3 BT is the correct version.

Is it connected WAN1 wise to either ADSL/VDSL ?

When does it restart, is it when the DSL syncs? Is there any pattern?

Is there a lot of configuration? I'd consider doing a factory reset and seeing if this resolves the issue and then manually reconfiguring.