Problem with internet via l2TP on home server under ubuntu server 12.04?

Question

linux

Given: Internet via L2tp dual access from Columbia Telecom, connected to the server. In the local network, a router as a WiFi access point and one computer. The Internet is connected to eth0, locale eth1.
Problem: The ppp0 interface falls off with increasing returns to the Internet, most often occurs when the torrent is actively working. When connecting the Internet directly to a local computer with Windows, the torrent with the same settings works fine.

/etc/network/interfaces

# The loopback network interface
auto lo
iface lo inet loopback

# The primary network interface
auto eth0
iface eth0 inet dhcp
up route add 83.167.66.16 gw 10.131.61.1  dev eth0 || true

up route add -net 83.167.64.0/19 gw 10.131.61.1 dev eth0 || true
up route add -net 10.0.0.0/8 gw 10.131.61.1 dev eth0 || true

auto eth1
iface eth1 inet static
address 192.168.0.2
netmask 255.255.255.0
post-up /etc/nat

/etc/nat

#!/bin/sh

#Разрешаем доступ из внутренней сети наружу
iptables -A FORWARD -i eth1 -o eth0 -j ACCEPT
iptables -A FORWARD -i eth1 -o ppp0 -j ACCEPT

#Включаем NAT
iptables -t nat -A POSTROUTING -o eth0 -s 192.168.0.0/24 -j MASQUERADE
iptables -t nat -A POSTROUTING -o ppp0 -s 192.168.0.0/24 -j MASQUERADE

#Разрешаем ответы из внешней сети
iptables -A FORWARD -i ppp0 -m state --state ESTABLISHED,RELATED -j ACCEPT

#Запрещаем доступ снаружи во внутреннюю сеть
iptables -A FORWARD -i ppp0 -o eth1 -j REJECT

/etc/xl2tpd/xl2tpd.conf

[lac nextone]
lns = l2tp.coltel.ru
redial = yes
redial timeout = 30
require chap = yes
require authentication = no
name = *****
ppp debug = yes
pppoptfile = /etc/ppp/options.l2tp
require pap = no
autodial = yes
rx bps = 100000000
tx bps = 100000000

/etc/ppp/options.l2tp

lock
noauth
nobsdcomp
nodeflate
nopcomp
noaccomp
nomppe
refuse-eap
refuse-pap
mru 1400
mtu 1400
name *****
remotename nextone
ipparam nextone
connect /bin/true
nopersist
maxfail 999
defaultroute
replacedefaultroute
unit 0

route-n

Destination Gateway Genmask Flags Metric Ref Use Iface
0.0.0.0         0.0.0.0         0.0.0.0         U     0      0        0 ppp0
10.0.0.0        10.131.61.1     255.0.0.0       UG    0      0        0 eth0
10.131.61.0     0.0.0.0         255.255.255.0   U     0      0        0 eth0
83.167.64.0     10.131.61.1     255.255.224.0   UG    0      0        0 eth0
83.167.65.0     10.131.61.1     255.255.255.0   UG    0      0        0 eth0
83.167.66.0     10.131.61.1     255.255.255.224 UG    0      0        0 eth0
83.167.66.16    10.131.61.1     255.255.255.255 UGH   0      0        0 eth0
83.167.66.16    0.0.0.0         255.255.255.255 UH    0      0        0 ppp0
192.168.0.0     0.0.0.0         255.255.255.0   U     0      0        0 eth1

With an increase in the load "on return", xl2tp swears in the logs:

grep xl2tp /var/log/syslog

Apr 13 00:33:32 ubuntu xl2tpd[1223]: udp_xmit failed to 83.167.66.16:1701 with err=-1:Resource temporarily unavailable
Apr 13 00:35:04  xl2tpd[1223]: last message repeated 123 times

like this a few times, then ppp0 falls off.
drops on eth0 appear in ifconfig

Answer 1

I think the problem is with the provider's servers. Many are now abandoning l2tp due to its instability and resource requirements.