So the line status is normal but the connection drops, right?
You are suggested to submit a ticket here with complete system log. Turn off the router first to clear the log and save the log after connection drops.
http://ticket.tp-link.com/index.php?/Tickets/Submit

I sent it back to the retailer Box.co.uk whos engineers after testing agreed it was faulty, unable to pick up an ip address they said, the modem kept intermittently losing sync / disconnecting from the internet, so i was sent a replacement & im having the same issues again but more frequently, yet my internet connection is fine since during the interim while waiting for my replacement i had a solid connection using my Asus RT66u & separate BT Modem, unless im very unlucky then TP-Link are making unreliable routers, im going to have to return this router back, its just not good enough

73 2015-10-26 06:54:42 PPP Information ppp1 sent [LCP ConfAck id=0xad ]
74 2015-10-26 06:54:42 PPP Information ppp1 rcvd [LCP ConfReq id=0xad ]
75 2015-10-26 06:54:42 PPP Information ppp1 sent [LCP ConfReq id=0x1 ]
76 2015-10-26 06:54:42 PPP Information ppp1 rcvd [PADS SessionID(0x8b03)]
77 2015-10-26 06:54:42 PPP Information ppp1 sent [PADR Host-Uniq(0x00000650)]
78 2015-10-26 06:54:42 PPP Information ppp1 rcvd [PADO PeerMac(00-30-88-00-00-08)]
79 2015-10-26 06:54:42 PPP Information ppp1 sent [PADI Host-Uniq(0x00000650)]
80 2015-10-26 06:54:18 PPP Error ppp1
81 2015-10-26 06:54:18 PPP Error ppp1 Timeout waiting for PADO packets
82 2015-10-26 06:53:58 PPP Information ppp1 sent [PADI Host-Uniq(0x0000059c)]
83 2015-10-26 06:53:48 PPP Information ppp1 sent [PADI Host-Uniq(0x0000059c)]
84 2015-10-26 06:53:46 DHCPD Notice Recv INFORM from C8:D7:19:1E:45:4C
85 2015-10-26 06:53:43 PPP Information ppp1 sent [PADI Host-Uniq(0x0000059c)]
86 2015-10-26 06:53:19 PPP Error ppp1
87 2015-10-26 06:53:19 PPP Error ppp1 Timeout waiting for PADO packets
88 2015-10-26 06:52:59 PPP Information ppp1 sent [PADI Host-Uniq(0x00000405)]
89 2015-10-26 06:52:54 DHCPD Notice Send ACK to 192.168.1.102
90 2015-10-26 06:52:54 DHCPD Notice Recv REQUEST from C8:D7:19:1E:45:4C
91 2015-10-26 06:52:49 PPP Information ppp1 sent [PADI Host-Uniq(0x00000405)]
92 2015-10-26 06:52:44 PPP Information ppp1 sent [PADI Host-Uniq(0x00000405)]
93 2015-10-26 06:52:25 PPP Error ppp1
94 2015-10-26 06:52:21 PPP Information ppp1 sent [LCP TermReq id=0x4 "User request"]
95 2015-10-26 06:52:18 PPP Information ppp1 sent [LCP TermReq id=0x3 "User request"]
96 2015-10-26 06:52:18 PPP Warning ppp1 LCP down
97 2015-10-26 06:52:18 PPP Error ppp1 LCP down
98 2015-10-26 06:52:18 PPP Error ppp1 User request
99 2015-10-26 06:38:46 DHCPD Notice Recv INFORM from C8:D7:19:1E:45:4C
100 2015-10-26 06:23:46 DHCPD Notice Recv INFORM from C8:D7:19:1E:45:4C
101 2015-10-26 06:09:48 DHCPD Notice Recv INFORM from C8:D7:19:1E:45:4C
102 2015-10-26 06:08:46 DHCPD Notice Recv INFORM from C8:D7:19:1E:45:4C
103 2015-10-26 05:58:32 DHCPD Notice Recv INFORM from C8:D7:19:1E:45:4C
104 2015-10-26 05:53:46 DHCPD Notice Recv INFORM from C8:D7:19:1E:45:4C

I've just had a reply back from TP Link support, its a known issue, i forwarded them all my logs showing PPP dropouts, errors & being unable to re-sync, im currently on my 2nd replacement which i will be returing to Box.co.uk for a refund, i've experienced the same modem PPP dropouts with them all & it not being able to resync

1st unit Box.co.uk RMA (R87623) > After testing the engineer stated it was unable to pick up an ip address.

2nd unit replacement Box.co.uk RMA (R88388) > The engineer found the wps feature not to be working as it should, no further testing was carried out in regards to modem connection issues

BTW, i tried putting the TP-Link into wireless mode & hooked up my BT ECI modem & i could not get it to connect to the the internet no matter which of the 4 LAN sockets i used, LAN 4 has WAN next to it so im guessing thats where you attach the ethernet cable from the modem? it wouldn't connect even after re-booting, so theres some serious issues with these routers whether its poor design or buggy firmware, who knows?

"Apologies for the problems caused to you by the TP-Link product.

We have already forwarded this case to our HQ and they are looking further into it.

We have received the similar feedback from other customers as well, regarding the VDSL Dropouts and Modem unable to synchronise again.

Would it be possible for you to provide me with the System Log files for the router, when it experiences dropouts and I will forward it to our HQ for further analysis. This will help us to get a more clearer picture of the issue.

Please Do keep me updated.

Melvit Cardozo

Technical support engineer

TP-Link UK Ltd."

I've just had a reply back from TP Link support, its a known issue, i forwarded them all my logs showing PPP dropouts, errors & being unable to re-sync, im currently on my 2nd replacement which i will be returing to Box.co.uk for a refund, i've experienced the same modem PPP dropouts with them all & it not being able to resync

1st unit Box.co.uk RMA (R87623) > After testing the engineer stated it was unable to pick up an ip address.

2nd unit replacement Box.co.uk RMA (R88388) > The engineer found the wps feature not to be working as it should, no further testing was carried out in regards to modem connection issues

BTW, i tried putting the TP-Link into wireless mode & hooked up my BT ECI modem & i could not get it to connect to the the internet no matter which of the 4 LAN sockets i used, LAN 4 has WAN next to it so im guessing thats where you attach the ethernet cable from the modem? it wouldn't connect even after re-booting yet when i connected up my Asus RT-N66U to the BT Moldem it worked fine, so theres some serious issues with these routers whether its poor design or buggy firmware, who knows?

"Apologies for the problems caused to you by the TP-Link product.

We have already forwarded this case to our HQ and they are looking further into it.

We have received the similar feedback from other customers as well, regarding the VDSL Dropouts and Modem unable to synchronise again.

Would it be possible for you to provide me with the System Log files for the router, when it experiences dropouts and I will forward it to our HQ for further analysis. This will help us to get a more clearer picture of the issue.

Please Do keep me updated.

Melvit Cardozo

Technical support engineer

TP-Link UK Ltd."