The DHCP (Dynamic Host Configuration Protocol) and BootP (Bootstrap Protocol) pass network configuration information to a host during startup. In NetDB3, DHCP is configured on node and network records. For node records, a unique hardware address must be entered to configure DHCP.
DHCP is also described in Internet RFCs 2131 and 2132. Note that BOOTP is a subset of DHCP commands.
DHCP information is updated from NetDB approximately every 10 minutes.
DHCP flag (node record)
When you check the DHCP box and enter a hardware address in NetDB, the campus DHCP servers will reply to a DHCP request from that address. The servers also return default DHCP options or additional options if they're specified in the NetDB record.
Roaming flag (node records)
Roaming DHCP allows machines to move to other networks without requiring manual configuration of IP addresses. If you check the Roaming box, you enable Roaming DHCP for that hardware address. If the machine moves to another network that offers available roaming DHCP addresses, the DHCP server will give one of these addresses to the mobile machine.
Default Node DHCP options
The default node DHCP options at Stanford University are IP address, subnet mask, gateway, domain name, and domain name servers. The option numbers come from RFCs 2131 and 2132.
|DHCP Option||Option Number||Description|
|IP Address||50||returns IP address assigned to requesting hardware address|
|Subnet mask||1||returns 255.255.0.0, in general|
|Gateway||3||for 171.64 addresses, returns 126.96.36.199; for 171.65 addresses, returns 188.8.131.52|
|Domain name||15||returns domain name asssigned to the Node|
|Domain name servers||6||184.108.40.206, 220.127.116.11 and 18.104.22.168 returned in random order|
Additional DHCP options
In NetDB, you can also set the following additional DHCP options for node interfaces, networks, or address spaces. Note: Use with caution as improper use may cause networking problems. The syntax for options is <dhcp option> = <value>.
|DHCP Option||Option Number||Node Interface||Net||Address Space||Description|
|tftp-server-name||66||Y||Y||Y||TFTP boot/config server|
|filename||67||Y||N||Y||boot/config file - e.g. thin clients|
|netbios-node-type||46||Y||Y||Y||1=B, 2=P, 4=M, 8=H|
|option-144||144||Y||N||N||for HP printers|
|default-lease-time||51||Y||Y||Y||DHCP lease time (currently 2 days)|
*By default, the DHCP service only responds to known clients — for example, nodes with their hardware addresses listed in NetDB. The permit DHCP option can override this default on a per-address space basis. A value of unknown-client allows both known and unknown clients to use DHCP in a particular address space; a value of only-unknown-client allows only unknown clients to use DHCP in a particular address space. The latter is useful for setting up networks with separate address spaces for known and unknown DHCP clients.
For more information, please submit a HelpSU ticket.