Arch Linux

Parameter

Member

From: Estonia

Registered: 2011-09-17

Posts: 3

[SOLVED] pppd: USB 3G modem problem

SOLVED: I finally got it fixed. The problem wasn't actually the pppd daemon nor arch linux, the problem was actually caused by my computer's BIOS. I had to enable PnP OS option in my BIOS, which causes the BIOS only configure essential devices (like bootable disks).

EDIT: The problem still wants to come back, although a lot rarer than it used to do

Hello! After failing to get my problem solved with the help of Google and some IRC, I finally decided to take a step forward and use the forums. Let me begin...

I am connecting to the internet via Huawei E1752 3G USB modem with pppd daemon. The kernel appears to be recognizing the modem nicely (except it thinks the modem is E169/E620/E800) and its mode appears to be switched. I can successfully connect to the internet, but the problem is that after several minutes (depending on the intensity of internet usage) the connection stops working. The light on the modem indicates it should be working with 3G speed. Also, the connection interrupts nearly every time after downloading a few files with pacman.

I've set up the pppd according to the arch linux wiki tutorials found at https://wiki.archlinux.org/index.php/3G … _with_pppd whereas:
1) /etc/ppp/peers/provider -> mobile-noauth
2) /etc/ppp/chatscripts/apn -> apn.ee.elisa, with content: AT+CGDCONT=1,"IP","internet"
3) /etc/ppp/chatscripts/mode --> mode.3G-pref
4) /etc/ppp/chatscripts/pin --> pin.NONE

A sample pppd session (a snippet of /var/log/messages.log):
http://paste.pocoo.org/show/477607/
I have set up dnsmasq and iptables to share the internet connection with another computer on the network. As you can see near the end of the log, the problem is with ISP not responding to echo-request (lcp-echo-failure is set to 5 and lcp-echo-interval to 30). I've tried to disable the echo-request feature, but this does not make a difference in connection's stability.

I also tried using wvdial, but it didn't work any better. The modem works flawlessly on the same system when used under Windows XP and with Huawei's own software.

If you need any additional details, please let me know, and I'll try to provide them.

Thanks in advance,
Parameter

Last edited by Parameter (2011-11-05 11:22:56)

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Estonian Programmer // Saxophonist // Pianist

brebs

Member

Registered: 2007-04-03

Posts: 3,742

Re: [SOLVED] pppd: USB 3G modem problem

There's lots of other PPP options for you to experiment with, e.g. I use these with a BlackBerry phone:

nodeflate
nobsdcomp
noaccomp

# Flow control - should be none, apparently.
nocrtscts
nocdtrcts

nomultilink
nopcomp
nomagic

ipcp-restart 7
ipcp-accept-local
ipcp-accept-remote

# From http://blog.ub3rgeek.net/2009/12/29/bluetooth-dun-with-blackberry-9700-t-mobile-and-ubuntu-9-10/
ipcp-max-configure 20

# Detect failure
#lcp-echo-interval 20
#lcp-echo-failure 3
# This removes failure detect
lcp-echo-interval 0
lcp-echo-failure 999

mtu 1492

921600

pap-timeout 20
pap-restart 20
lcp-restart 10

holdoff 2
modem
persist

In particular, try the 2 lcp-echo lines I'm using.

Parameter

Member

From: Estonia

Registered: 2011-09-17

Posts: 3

Re: [SOLVED] pppd: USB 3G modem problem

Wow, it has been long time since I have posted on this topic...

Anyways, thank you for replying. Although the config file you posted didn't eliminate the problem, it still helped make the connection time noticeably longer. the two lcp-echo lines actually made it worse. From recent experiments, manipulating with mtu/mru and baud rates seemed to variate the connection time. Well, I started with plain configuration and am adding some options step-by-step to see if anything helps.

Any suggestions will be greatly appreciated to further ease the troubleshooting...

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Estonian Programmer // Saxophonist // Pianist