У меня такая ситуация поставил себе модем 2500u, обновил прошивку до RU_DSL-2500U_3-06-04-2100.A2pB021c.d19b гдето месяц полтора он нормально проработал а буквально неделю назад начал дисконектиться т.е. включаю комп модем заходит в интернет ...нормально работаю от 2-6 часов а потом обрывается и начинает заново линковать если заново подлинковывается то хорошо но очень часто начинает линковать кажется что вотвот загорится лампа линк но она обрывается и опять начинает линковать и так до бесконечности....помогает вроде выключение модема и компа на несколько часов а потом включение....оператор - ютк, звонил они говорят что у них все в норме и диагностировали линию они сказали что удовлетворительно...но обрывы щас очень часто идут и что самое плохое заново не полинковывается, подскажите что делать...прошивка вроде итак последняя стоит....

Приведите вывод страницы Status > ADSL, приведите логи модема в моменты разрывов.

ADSL Statistics

Mode: ADSL2
Line Coding: Trellis On
Status: No Defect
Link Power State: L0

Downstream Upstream
SNR Margin (dB): 6.9 9.0
Attenuation (dB): 46.0 32.9
Output Power (dBm): 12.8 1.1
Attainable Rate (Kbps): 1484 736
Rate (Kbps): 608 637
MSGc (number of bytes in overhead channel message): 40 104
B (number of bytes in Mux Data Frame): 13 13
M (number of Mux Data Frames in FEC Data Frame): 16 16
T (Mux Data Frames over sync bytes): 2 1
R (number of check bytes in FEC Data Frame): 16 16
S (ratio of FEC over PMD Data Frame length): 11.3609 10.4348
L (number of bits in PMD Data Frame): 169 184
D (interleaver depth): 2 1
Delay (msec): 5 2

Super Frames: 410009 410007
Super Frame Errors: 172347 671
RS Words: 2357552 1742529
RS Correctable Errors: 728644 1235
RS Uncorrectable Errors: 409144 N/A

HEC Errors: 135819 1075
OCD Errors: 24 0
LCD Errors: 0 0
Total Cells: 9358537 10063212
Data Cells: 90939 504416
Bit Errors: 0 0

Total ES: 9395 213
Total SES: 5220 10
Total UAS: 1314 37
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Jan 1 05:19:55 user debug syslog: iptables -t nat -D POSTROUTING -o ppp_0_35_1 -s 192.168.1.0/255.255.255.0 -j MASQUERADE 2>/dev/null
Jan 1 05:19:55 user debug syslog: iptables -t nat -A POSTROUTING -o ppp_0_35_1 -s 192.168.1.0/255.255.255.0 -j MASQUERADE
Jan 1 05:20:07 daemon notice pppd[237]: PPP: Start to connect ...
Jan 1 05:20:11 daemon crit pppd[237]: PPP LCP UP.
Jan 1 05:20:17 daemon crit pppd[237]: Received valid IP address from server. Connection UP.
Jan 1 05:20:17 user debug syslog: route add default gw 87.117.48.1 2>/dev/null
Jan 1 05:20:17 user debug syslog: route add -net 10.253.0.0 netmask 255.255.255.0 metric 1 gw 10.253.44.1 2>/dev/null
Jan 1 05:20:17 user debug syslog: iptables -A FORWARD -o ppp_0_35_1 -p tcp --tcp-flags SYN,RST SYN -j TCPMSS --set-mss 1452
Jan 1 05:20:17 user debug syslog: iptables -A FORWARD -i ppp_0_35_1 -p tcp --tcp-flags SYN,RST SYN -j TCPMSS --set-mss 1452
Jan 1 05:20:17 user debug syslog: iptables -t nat -D POSTROUTING -o ppp_0_35_1 -s 192.168.1.0/255.255.255.0 -j MASQUERADE 2>/dev/null
Jan 1 05:20:17 user debug syslog: iptables -t nat -A POSTROUTING -o ppp_0_35_1 -s 192.168.1.0/255.255.255.0 -j MASQUERADE
Jan 1 05:20:17 user warn dnsprobe[589]: dns query failed
Jan 1 05:20:18 user notice dnsprobe[589]: Switching Back To Primary DNS server
Jan 1 05:20:51 user warn dnsprobe[589]: dns query failed
Jan 1 05:20:53 user warn dnsprobe[589]: dns query failed
Jan 1 05:20:55 user warn dnsprobe[589]: dns query failed
Jan 1 05:20:55 user notice dnsprobe[589]: Primary DNS server Is Down... Switching To Secondary DNS server
Jan 1 05:21:27 user warn dnsprobe[589]: dns query failed
Jan 1 05:21:28 user notice dnsprobe[589]: Switching Back To Primary DNS server
Jan 1 05:22:35 daemon crit pppd[237]: Clear IP addresses. Connection DOWN.
Jan 1 05:22:35 daemon crit pppd[237]: Clear IP addresses. PPP connection DOWN.
Jan 1 05:22:41 daemon notice pppd[237]: PPP: Start to connect ...
Jan 1 05:22:49 daemon crit pppd[237]: PPP LCP UP.
Jan 1 05:23:02 user warn dnsprobe[589]: dns query failed
Jan 1 05:23:03 daemon notice pppd[237]: PPP: Start to connect ...
Jan 1 05:23:04 user warn dnsprobe[589]: dns query failed
Jan 1 05:23:06 user warn dnsprobe[589]: dns query failed
Jan 1 05:23:06 user notice dnsprobe[589]: Primary DNS server Is Down... Switching To Secondary DNS server
Jan 1 05:23:06 daemon crit pppd[237]: PPP LCP UP.
Jan 1 05:23:14 daemon crit pppd[237]: Received valid IP address from server. Connection UP.
Jan 1 05:23:14 user debug syslog: route add default gw 87.117.48.1 2>/dev/null
Jan 1 05:23:14 user debug syslog: route add -net 10.253.0.0 netmask 255.255.255.0 metric 1 gw 10.253.44.1 2>/dev/null
Jan 1 05:23:14 user debug syslog: iptables -A FORWARD -o ppp_0_35_1 -p tcp --tcp-flags SYN,RST SYN -j TCPMSS --set-mss 1452
Jan 1 05:23:15 user debug syslog: iptables -A FORWARD -i ppp_0_35_1 -p tcp --tcp-flags SYN,RST SYN -j TCPMSS --set-mss 1452
Jan 1 05:23:15 user debug syslog: iptables -t nat -D POSTROUTING -o ppp_0_35_1 -s 192.168.1.0/255.255.255.0 -j MASQUERADE 2>/dev/null
Jan 1 05:23:15 user debug syslog: iptables -t nat -A POSTROUTING -o ppp_0_35_1 -s 192.168.1.0/255.255.255.0 -j MASQUERADE
Jan 1 05:23:38 user warn dnsprobe[589]: dns query failed
Jan 1 05:23:39 user notice dnsprobe[589]: Switching Back To Primary DNS server
Jan 1 05:24:11 user warn dnsprobe[589]: dns query failed
Jan 1 05:24:13 user warn dnsprobe[589]: dns query failed
Jan 1 05:24:46 user warn dnsprobe[589]: dns query failed
Jan 1 05:25:19 user warn dnsprobe[589]: dns query failed
Jan 1 05:25:21 user warn dnsprobe[589]: dns query failed
Jan 1 05:26:25 user warn dnsprobe[589]: dns query failed
Jan 1 05:26:27 user warn dnsprobe[589]: dns query failed
Jan 1 05:26:29 user warn dnsprobe[589]: dns query failed
Jan 1 05:26:29 user notice dnsprobe[589]: Primary DNS server Is Down... Switching To Secondary DNS server
Jan 1 05:27:02 user warn dnsprobe[589]: dns query failed
Jan 1 05:27:03 user notice dnsprobe[589]: Switching Back To Primary DNS server
Jan 1 05:28:06 user warn dnsprobe[589]: dns query failed
Jan 1 05:28:08 user warn dnsprobe[589]: dns query failed
Jan 1 05:28:10 user warn dnsprobe[589]: dns query failed
Jan 1 05:28:10 user notice dnsprobe[589]: Primary DNS server Is Down... Switching To Secondary DNS server
Jan 1 05:28:41 user notice dnsprobe[589]: Switching Back To Primary DNS server
Jan 1 05:29:13 user warn dnsprobe[589]: dns query failed
Jan 1 05:29:15 user warn dnsprobe[589]: dns query failed
Jan 1 05:29:17 user warn dnsprobe[589]: dns query failed
Jan 1 05:29:17 user notice dnsprobe[589]: Primary DNS server Is Down... Switching To Secondary DNS server
Jan 1 05:29:48 user notice dnsprobe[589]: Switching Back To Primary DNS server
Jan 1 05:30:20 user warn dnsprobe[589]: dns query failed
Jan 1 05:31:24 user warn dnsprobe[589]: dns query failed
Jan 1 05:31:57 user warn dnsprobe[589]: dns query failed
Jan 1 05:32:31 user warn dnsprobe[589]: dns query failed
Jan 1 05:32:33 user warn dnsprobe[589]: dns query failed
Jan 1 05:32:35 user warn dnsprobe[589]: dns query failed
Jan 1 05:32:35 user notice dnsprobe[589]: Primary DNS server Is Down... Switching To Secondary DNS server
Jan 1 05:33:06 user notice dnsprobe[589]: Switching Back To Primary DNS server
Jan 1 05:34:09 user warn dnsprobe[589]: dns query failed
Jan 1 05:34:42 user warn dnsprobe[589]: dns query failed
Jan 1 05:34:44 user warn dnsprobe[589]: dns query failed
Jan 1 05:34:46 user warn dnsprobe[589]: dns query failed
Jan 1 05:34:46 user notice dnsprobe[589]: Primary DNS server Is Down... Switching To Secondary DNS server
Jan 1 05:35:17 user notice dnsprobe[589]: Switching Back To Primary DNS server
Jan 1 05:37:53 user warn dnsprobe[589]: dns query failed
Jan 1 05:39:28 user warn dnsprobe[589]: dns query failed
Jan 1 05:39:30 user warn dnsprobe[589]: dns query failed
Jan 1 05:40:03 user warn dnsprobe[589]: dns query failed
Jan 1 05:41:07 user warn dnsprobe[589]: dns query failed
Jan 1 05:48:23 user warn dnsprobe[589]: dns query failed
Jan 1 06:00:12 syslog info -- MARK --
Jan 1 06:04:27 user warn dnsprobe[589]: dns query failed
Jan 1 06:04:29 user warn dnsprobe[589]: dns query failed
Jan 1 06:04:31 user warn dnsprobe[589]: dns query failed
Jan 1 06:04:31 user notice dnsprobe[589]: Primary DNS server Is Down... Switching To Secondary DNS server
Jan 1 06:05:02 user notice dnsprobe[589]: Switching Back To Primary DNS server
Jan 1 06:12:48 user warn dnsprobe[589]: dns query failed
Jan 1 06:12:50 user warn dnsprobe[589]: dns query failed
Jan 1 06:12:52 user warn dnsprobe[589]: dns query failed
Jan 1 06:12:52 user notice dnsprobe[589]: Primary DNS server Is Down... Switching To Secondary DNS server
Jan 1 06:13:23 user notice dnsprobe[589]: Switching Back To Primary DNS server
Jan 1 06:26:51 user warn dnsprobe[589]: dns query failed
вроде так...

Очень большое затухание в телефонной линии и слишком малое отношение сигнал/шум, что является причиной разрывов.
Попросите провайдера немного понизить скорость Downstream потока (при этом SNR должен возрасти, а Attenuation - понизиться), cоответственно, связь станет стабильней. Пусть также включат режим Interleave и задержку в передаче данных сделают побольше.

вот произошел реконект и не сразу линкует модем в логе пишет:
Jan 1 00:00:12 user crit kernel: ADSL G.994 training
Jan 1 00:00:12 user debug syslog: tftpd
Jan 1 00:00:13 user debug syslog: pppd
Jan 1 00:00:14 daemon notice pppd[237]: pppd 2.4.1 started by admin, uid 0
Jan 1 00:00:28 user crit kernel: ADSL G.992 started
Jan 1 00:00:29 user crit kernel: ADSL link down
Jan 1 00:00:32 user crit kernel: ADSL G.994 training
Jan 1 00:00:37 user crit kernel: ADSL G.992 started
Jan 1 00:00:38 user crit kernel: ADSL link down
Jan 1 00:00:41 user crit kernel: ADSL G.994 training
Jan 1 00:00:46 user crit kernel: ADSL G.992 started
Jan 1 00:00:47 user crit kernel: ADSL link down
Jan 1 00:00:49 user crit kernel: ADSL G.994 training
Jan 1 00:00:55 user crit kernel: ADSL G.992 started
Jan 1 00:00:59 user crit kernel: ADSL G.992 channel analysis
Jan 1 00:01:03 user crit kernel: ADSL G.992 message exchange
Jan 1 00:01:03 user crit kernel: ADSL link up, interleaved, us=637, ds=567
Jan 1 00:01:03 user warn kernel: ATM Soft SAR: ATM link connected.
Jan 1 00:01:04 user debug syslog: iptables -t nat -A PREROUTING -i br0 -d 192.168.1.1 -p udp --dport 53 -j DNAT --to 128.9.0.107
Jan 1 00:01:05 daemon notice pppd[237]: PPP: Start to connect ...
Jan 1 00:01:08 daemon crit pppd[237]: PPP LCP UP.
Jan 1 00:01:09 daemon crit pppd[237]: Received valid IP address from server. Connection UP.
Jan 1 00:01:09 user debug syslog: route add default gw 87.117.48.1 2>/dev/null
причем про кернел красным....и еще такой момент захожу в интернет скорость вроде нормальная но буквально минут через 20 скорость ощутимо на глазах начинает падать т.е. сайты еле открываются....то что вы написали я щас позвоню прову конечно а это поможет? или может лучше купить модем 500т?

Читайте выше.

Отстой и геморой это, а не линия.