Friday, March 13, 2015

IPv6 Internet access from IPv4 (BSNL) DSL Connection

As of now AFAIK BSNL, the largest ISP in India, is not providing IPv6 Internet to DSL home users. So here is a cool way to connect to IPv6 Internet using a IPv4 DSL connection.

I have a BSNL DSL Broadband connection with dynamic IPv4 address with NAT.
Here I will demonstrate a way to access IPv6 Internet using a IPv6-over-IPv4 tunnel from tunnel broker Hurrican Electric. I am running Ubuntu Linux 14.04.


Signup with any IPv6 tunnel brokers in internet like Hurrican Electric or SixxS. Create a regular IPv6 tunnel. Add v4tunnel interface configuration in our computer.

Friday, October 17, 2014

Enabling developer options in Android 4.1+

Developer options like USB debugging are by default disabled in Android 4.1+ ( Android 4.2, Android 4.4.4) and the menu to enable is hidden!.

To Enable Developer Options:

  1. Go to "Settings"

Wednesday, October 15, 2014

Extract data from .dbk backup of Sony Xperia

Sometimes it happens that restoring from a .dbk backup fails (especially after flashing a custom ROM). You can extract data like contacts, messages etc from .dbk file as follows:

  1. Locate .dbk file. If you took backup using Sony PC Companion, Default backup folder is C:\Users\USERNAME\Documents\Sony\Sony PC Companion\Phone backups .
  2. Copy .dbk file to Desktop.
  3. Rename .dbk to .zip. Say Original file be XYZ.dbk , Rename to
  4. Extract using any unzip softwares ( Eg: WinRAR, 7zip etc)
  5. In Extracted contents, See "Applications" Folder. Inside it, Each data type will have separate folders. To Extract contacts, Go inside "" folder and copy "fullbackupdata" file to Desktop. This is the compressed archive of all contacts.
  6. This "fullbackupdata" can be extracted using restoreData.jar . Download jar file from Keep jar file in same folder as "fullbackupdata". NOTE: If you cannot find restoreData.jar file at this link, Just Google it.
  7. Now run jar file. It will output a restore.tar file. Note: To run .jar file you should be having JAVA installed.
  8. This tar file can be extracted using any Unzip programs ( WinRAR, 7zip etc) . Inside you can find the full_backup_vcard.vcf VCard File which can be imported into phone contacts. Note: For importing to Phone, Copy this file to your sdcard. In phone, Go to Contacts -> import/export -> Import from storage


Johannes Deml and Nikolay Elenkov

Sunday, July 06, 2014

Enabling SSH and block Telnet in Cisco Routers/Switches

SSH protocol encrypts the traffic between client and server in a remote session. So for network security purpose, we should enable only SSH access to networking devices.

Before enabling SSH, make sure we configured hostname and domain name properly. This will be used to store the name of the RSA key pair generated.  All the configurations are to be done in Global config mode.

hostname Router1
ip domain name

Change hostname and '' domain name to your organization domain name. Now generate the RSA keys for SSH

crypto key generate rsa

This will ask the number of bits required for modulus function. Default is 512 bits but if we want to enable SSH version 2, bits should be more than 768. So, better keep 1024 bits.

Thursday, June 12, 2014

Setting up a Syslog server in Ubuntu for Cisco routers/switches

Configuration to be done in Ubuntu server

RSYSLOG is the default logging utility in Ubuntu. Main configuration file for rsyslog is /etc/rsyslog.conf. Make sure that there is a line as follows in the rsyslog.conf file.
$IncludeConfig /etc/rsyslog.d/*.conf
Now make a new file (say cisco.conf) in /etc/rsyslog.d directory.
Add these line to cisco.conf
local7.*    /var/log/cisco/cisco.log
This means that all syslog messages with facility (or tag) as local7 (Local7 is the default tag on all syslog messages from cisco devices) should be logged to cisco.log file at /var/log/cisco directory. So create a folder named cisco at /var/log and a blank document cisco.log inside that folder.
Now just restart rsyslog daemon using the command
sudo service rsyslog restart

Configuration to be done in Cisco device

In the Cisco router/switch whose logs are to be logged in the syslog server, configure the following :

logging Ubuntu_Server_IP
For example,
Now all the logs from Cisco device will be logged to Syslog server in the Ubuntu machine. You can see the logs at System Log viewer by opening /var/log/cisco/cisco.log

Show running-config as read-only in Cisco routers without using AAA with TACACS+ and RADIUS

Sometimes it happens that we have to provide read only access to the running configuration of routers to someone who has a lower privilege. Cisco defines privilege level 15 as full access privileged EXEC mode and privilege level 1 as the normal user exec mode. In between levels are not defined by default. We can use privilege command to move commands from one privilege level to another.

privilege exec all level 10 show running-config

alias exec shrun show running-config view full

username hdesk privilege 10 secret hdesk@1234

  1. Move show running-config command to a privilege level 10
  2. But to view the running configuration, instead of show running-config, we have to type complete show running-config view full. So let's create a alias named shrun. This is optional.
  3. Now create a user with the privilege level 10. This user will be now able to see running configuration using the alias command shrun .