Net tools was replaced with iproute2 as net tools seems to be unmaintained. Iproute2 doesn't have the ifconfig command but it should have an equivalent. I don't know what that is as I stayed with net tools. It wasn't causing me any problems so I thought, if it ain't broke, don't fix it. I know, I should be cool, bleeding edge and all that but sometimes I can't be arsed.
You could read man ip to try and figure out how to use iproute2 or if you want net tools the instructions are in BLFS. This is the thread where they discussed the change to the book back in June
http://linuxfromscratch.org/pipermai...ne/046960.html