DHCP assignment:
- Lease Request: Client broadcasts request to DHCP server with a source address of 0.0.0.0 and a destination address of 255.255.255.255. The request includes the MAC address which is used to direct the reply.
- IP lease offer: DHCP server replies with an IP address, subnet mask, network gateway, name of the domain, name servers, duration of the lease and the IP address of the DHCP server.
- Lease Selection: Client recieves offer and broadcasts to al DHCPservers that will accept given offer so that other DHCP server need not make an offer.
- The DHCP server then sends an ack to the client. The client is configured to use TCP/IP.
- Lease Renewal: When half of the lease time has expired, the client will issue a new request to the DHCP server.
(or /etc/rc.d/init.d/dhcpd start for Red Hat, Fedora and CentOS Linux distributions)
Sample DHCP server config file: (DHCP v3.0.1) /etc/dhcpd.conf
(See /usr/share/doc/dhcp-3.X/dhcp.
ddns-update-style interim; # Required for dhcp 3.0+ / Red Hat 8.0+ ignore client-updates; subnet 192.168.1.0 netmask 255.255.255.0 { range 192.168.1.128 192.168.1.254; # Range of IP addresses to be issued to DHCP clients option subnet-mask 255.255.255.0; # Default subnet mask to be used by DHCP clients option broadcast-address 192.168.1.255; # Default broadcastaddress to be used by DHCP clients option routers 192.168.1.1; # Default gateway to be used by DHCP clients option domain-name "your-domain.org"; option domain-name-servers 40.175.42.254, 40.175.42.253; # Default DNS to be used by DHCP clients option netbios-name-servers 192.168.1.100; # Specify a WINS server for MS/Windows clients. # (Optional. Specify if used on your network) # DHCP requests are not forwarded. Applies when there is more than one ethernet device and forwarding is configured. # option ipforwarding off; default-lease-time 21600; # Amount of time in seconds that a client may keep the IP address max-lease-time 43200; option time-offset -18000; # Eastern Standard Time # option ntp-servers 192.168.1.1; # Default NTP server to be used by DHCP clients # option netbios-name-servers 192.168.1.1; # --- Selects point-to-point node (default is hybrid). Don't change this unless you understand Netbios very well # option netbios-node-type 2; # We want the nameserver "ns2" to appear at a fixed address. # Name server with this specified MAC address will recieve this IP. host ns2 { next-server ns2.your-domain.com; hardware ethernet 00:02:c3:d0:e5:83; fixed-address 40.175.42.254; } # Laser printer obtains IP address via DHCP. This assures that the # printer with this MAC address will get this IP address every time. host laser-printer-lex1 { hardware ethernet 08:00:2b:4c:a3:82; fixed-address 192.168.1.120; } }
can be obtained with the command /sbin/ifconfig:
eth0 Link encap:Ethernet HWaddr 00:02:C3:D0:E5:83 inet addr:40.175.42.254 Bcast:40.175.42.255 Mask:255.255.255.0 inet6 addr: fe80::202:b3ff:fef0:e484/64 Scope:Link UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1 RX packets:4070 errors:0 dropped:0 overruns:0 frame:0 TX packets:3878 errors:0 dropped:0 overruns:0 carrier:0 collisions:0 txqueuelen:1000 RX bytes:3406445 (3.2 MiB) TX bytes:439612 (429.3 KiB)
lease 192.168.1.128 { starts 2 2004/12/01 20:07:05; ends 3 2004/12/02 08:07:05; hardware ethernet 00:00:e8:4a:2c:5c; uid 01:00:00:e8:4c:5d:31; client-hostname "Node1"; }