[ubuntu] How to change default network configuration in ubuntu 12.04.1

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http://ubuntuforums.org – One change in ubuntu 12.04.1 from 10.04 is that the OS checks for network config at the time of booting and perhaps wants to completes network connection before the log in screen is visible. However I use modem along with telephone line to connect to internet and till 10.04 I used to connect modem after logging into my account. This is no longer the default way in 12.04. The OS patiently tries to complete net-config and failing that, waits for "one more minute" to complete as last effort to complete but all this is useless and annoying for me since I know the process is not going to (Hardware)