Ubuntu 安裝 DHCP Server

dhcp3-server is a dummy package which wraps the real isc-dhcp-server package.

許多舊的關於 Ubuntu DHCP Server 教學文件都是不符合現狀的。
Ubuntu 11.04 內的 dhcp3-server 根本就是幌子！

真正的 DHCP 服務名稱既不是 dhcpd 也不是 dhcp3-server，而是 isc-dhcp-server。

Internet Systems Consortium, Inc. (ISC) is proud to be the producer and distributor of commercial quality Open Source software for the Internet Community and to offer world-class online and professional services based on our software.

sudo apt-get install isc-dhcp-server

設定檔：
/etc/dhcp/dhcp.conf
/etc/defaults/isc-dhcp-server

記錄檔：
/var/lib/dhcp/dhcpd.leases
/var/log/syslog

啟動腳本：
/etc/init.d/isc-dhcp-server

有多張網卡在 DHCP Server 上的需要特別注意：

When a DHCP configured PC boots, it requests its IP address from the DHCP server. It does this by sending a standardized DHCP broadcast request packet to the DHCP server with a source IP address of 255.255.255.255.
If your DHCP server has more than one interface, you have to add a route for this 255.255.255.255 address so that it knows the interface on which to send the reply.

Reference：
http://ubuntuforums.org/showthread.php?t=1754623
http://manpages.ubuntu.com/manpages/natty/man8/dhcp-helper.8.html
http://prefetch.net/articles/iscdhcpd.html
http://www.linuxhomenetworking.com/wiki/index.php/Quick_HOWTO_:_Ch08_:_Configuring_the_DHCP_Server