Configuring your DSL modem through your router

I unplugged my modem last week before I went to Dortmund for some days and plugged it back in last Sunday when I came back. Since then my DSL broadband access is pretty slow. Like 1 Mbit/s downstream, should be around 16 Mbit/s. Therefore I messed a little bit around with my configuration and found out that my DSL Modem – Siemens C2-010-I, is actually Viking II Plus and not a modem but a moden/router/bridge. My provider configured the Viking as a bridge, therefore it looked like a usual DSL modem.

Basically you just have to configure your interface on your PC to have the IP-Address (or any other address within and then you either can access the Viking’s HTTP or telnet server via

With the web interface running on the HTTP server you can configure basic things like switching your bridging modem into a router. The basic configurations options you have for every DSL router. Anyway more interesting is the telnet interface. With the help of it you can get many more informations about your DSL connection. I found a preliminary command reference for the Viking chip set family which seems to contains many commands you can use to get some more informations out of your modem/router/bridge.

martin@kovalski:~$ telnet
Connected to
Escape character is '^]'.


Software Release R100B01.0B_HN_20060406
Copyright (c) 2001-2004

login: alice@13184
Login Successful
Command Description
------- -----------
alias To Alias a command
apply Apply configuration/image file
commit Commit the active config to the flash
create Create a new entry of specified type
delete Delete the specified entry
download Download a file on to the Device
exit To exit the CLI shell
get Display info for the search
help Provides help
list List files
modify Modify information for specified entry
passwd To modify user password
ping The normal ping command
prompt Change the user prompt
reboot Reboot the device
remove Remove file
reset Reset info for the specified entry
size ATM Sizing Information
traceroute The normal traceroute command
trigger To set trigger
unalias To undefine previously defined alias
verbose Switch ON/OFF the verbose mode
$get dsl stats curr

No. of 15 Min. Valid Data Intervals : 6
No. of 15 Min. Invalid Data Intervals : 0
Current 15 Min. Elapsed Time (MM:SS) : 6:56
Current 15 Min. Errored Seconds : 0
Current 15 Min. Sev Errored Seconds : 0
Current 15 Min. Unavailable Seconds : 0
Current Day Elapsed Time (HH:MM:SS) : 1:51:56
Current Day Errored Seconds : 0
Current Day Sev Errored Seconds : 0
Current Day Unavailable Seconds : 38
Previous Day Monitored Time (HH:MM:SS) : 0:0:0
Previous Day Errored Seconds : 0
Previous Day Sev Errored Seconds : 0
Previous Day Unavailable Seconds : 0
$get dsl params

Vendor ID : 0039
Revision Number : E.37.2.8
Serial number : 123456789abcdx
Self Test : Passed Framing Structure : Unknown
Standard : ADSL2/2+ Trellis Coding : -
Local Tx. Power(dB) : 12.6 Remote Tx.Power(dB) : 0.0
Local Line Atten(dB) : 18.5 Remote Line Atten(dB) : 11.5
Local SNR Margin(dB) : 12.5 Remote SNR Margin(dB) : 6.5
Tx Line Rate(kbps) : 0 Rx Line Rate(kbps) : 0
Up SValue : - Down SValue : -
Up DValue : - Down DValue : -
Data Boost : - Max Att. DnS LR(kbps) : 0

UpIntrlvd UpFast DownIntrlvd DownFast
AS0(kbps): - - - -
AS1(kbps): - - - -
LS0(kbps): - - - -
LS1(kbps): - - - -
RValue : - - - -

Anyway… now that you are able to get some informations out of your DSL modem/router. I actually like my OpenWrt based router…. damn…

…. writing this I just realized that this whole problem might not be related to my broadband provide – you remember, I just wanted to figure out why my connection was so slow before I tried to mess around with my modem – but to the not configured QOS settings of my so beloved OpenWrt router. Before I went to Dortmund my router got a little software update. Check, confirmed. QOS disabled.

… now that I have my whole bandwidth back… what was the point… right: I love my OpenWrt router. So I like to keep the bridge configuration but want to be able to access the DSL modem/router/bridge from within my local network behind my OpenWrt router. Therefore I have to adjust the firewall configuration a little. First make sure, that your modem and your router are not in the same subnet. I decided to configure my router to be and the modem to stay as

Now, the adjustment of the router’s firewall:

martin@kovalski:~$ ssh root@
root@'s password:

BusyBox v1.4.2 (2008-10-01 22:05:02 CEST) Built-in shell (ash)
Enter 'help' for a list of built-in commands.

_______ ________ __
| |.-----.-----.-----.| | | |.----.| |_
| - || _ | -__| || | | || _|| _|
|_______|| __|_____|__|__||________||__| |____|
|__| W I R E L E S S F R E E D O M
KAMIKAZE (7.09) -----------------------------------
* 10 oz Vodka Shake well with ice and strain
* 10 oz Triple sec mixture into 10 shot glasses.
* 10 oz lime juice Salute!
root@SRB178:~# ifconfig eth0.1 up
root@SRB178:~# iptables -t nat -A postrouting_rule -o eth0.1 -d -j MASQUERADE
root@SRB178:~# iptables -A forwarding_rule -i br-lan -o eth0.1 -p tcp --dport 80 -d -j ACCEPT
root@SRB178:~# iptables -A forwarding_rule -i br-lan -o eth0.1 -p tcp --dport 23 -d -j ACCEPT

First configure your WAN interface. Then the firewall: The first rule is to masquerade the traffic from as The modem/router does not know anything about the network. It will receive the requests out of the network but does not know where to send them back.
The other two rules are to allow the forwarding of traffic from the internal network to the modem/router on port 80 (http) and 23 (telnet).

If you want to get the informations easier than manually telnet into the modem and send the commands you can also use the fancy DSL-Modem Tool. There are several versions of this tool for different modems, but basically they all seem to use telnet to gather the informations.

By the way, the user name and password for accessing my modem were:
User: alice@13184 password: hnto$mgmt@lice
This is the default configuration of my broadband provider Alice.


2 thoughts on “Configuring your DSL modem through your router”

  1. hi, i’m trying to debug a connection with a viking modem as well. where did you find the command reference? thank you!

  2. You mean the command reference of the viking modem? You can use the help command to get descriptions of the different commands, or you could just use the tool from DSL Modem Tool from

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