DHCP server file known options

Edit online

The known options of the DHCP server file are identified here.

Note: The options that are shown in this table as not allowed to be specified (No in the Can Specify? column) can be specified in the configuration file, but are overwritten by the correct value. For a better definition of each option, see RFC 2132.
Option Number Default Data Type Can Specify? Description/Use
0 None No The server pads the option field, if necessary.
1 Dotted quad No The net mask of the subnet from which the address was drawn.
2 32-bit integer Yes Specifies the offset of the client subnet, in seconds from Coordinated Universal Time (UTC).
3 One or more dotted quads Yes A list of the default gateways' IP addresses.
4 One or more dotted quads Yes A list of time server IP addresses.
5 One or more dotted quads Yes A list of name server IP addresses.
6 One or more dotted quads Yes A list of DNS IP addresses.
7 One or more dotted quads Yes A list of log server IP addresses.
8 One or more dotted quads Yes A list of cookie server IP addresses.
9 One or more dotted quads Yes A list of LPR server IP addresses.
10 One or more dotted quads Yes A list of Impress server IP addresses.
11 One or more dotted quads Yes A list of Resource Location server IP addresses.
12 An ASCII string Yes A host name for the client to use.
13 16-bit unsigned integer Yes The size of the bootfile.
14 An ASCII string Yes The path for Merit Dump file.
15 An ASCII string Yes The default DNS domain name.
16 An IP address Yes The address of the Swap server.
17 An ASCII string Yes The default root path.
18 An ASCII string Yes The path to extensions for the client.
19 Yes, No, True, False, 1, 0 Yes Specify whether IP Forwarding should be turned on.
20 Yes, No, True, False, 1, 0 Yes Specify whether non-local source routing should be used.
21 One or more pairs of dotted quads, in the form DottedQuad:DottedQuad Yes The filter policies for IP addresses.
22 16-bit unsigned integer Yes The maximum size to allow for datagram fragments.
23 8-bit unsigned integer Yes The IP time-to-live (TTL).
24 32-bit unsigned integer Yes The number of seconds to use in the Path MTU aging timeout.
25 List of one or more 16-bit unsigned integers Yes The path MTU Plateau table. Specifies a set of values that represent the MTU sizes to use when using Path MTU discovery.
26 16-bit unsigned integer Yes Specifies MTU size for the receiving interface.
27 Yes, No, True, False, 1, 0 Yes Specifies whether all subnets are local.
28 An IP address (dotted quad) Yes Specifies broadcast address for the interface.
29 Yes, No, True, False, 1, 0 Yes Specifies whether ICMP netmask discovery should be used.
30 Yes, No, True, False, 1, 0 Yes Specifies whether client should become an ICMP netmask supplier.
31 Yes, No, True, False, 1, 0 Yes Specifies whether ICMP Router Discovery messages should be used.
32 IP address (dotted quad) Yes Specifies address to use for router solicitation.
33 One or more IP address pairs, in the form DottedQuad:DottedQuad Yes Each address pair represents a static route.
34 Yes/No, True/False, 1/0 Yes Specifies whether trailer encapsulation should be used.
35 32-bit unsigned integer Yes ARP cache timeout value.
36 Yes/No, True/False, 1/0 Yes Specifies whether Ethernet encapsulation should be used.
37 8-bit unsigned integer Yes The TCP time-to-live (TTL).
38 32-bit unsigned integer Yes The TCP keep alive interval.
39 Yes/No, True/False, 1/0 Yes Specifies whether TCP keep alive should be used.
40 An ASCII string Yes The NIS default domain.
41 One or more dotted quads Yes Specifies the IP addresses of the NIS servers.
42 One or more dotted quads Yes Specifies the IP addresses of the NTP servers.
43 hex string of digits, in the form of hex "digits", hex "digits", or 0xdigits Yes, but really only specified with vendor container Encapsulated option container for the vendor container.
44 One or more dotted quads Yes Specifies NetBIOS name server IP addresses.
45 One or more dotted quads Yes Specifies NetBIOS datagram distribution server IP addresses.
46 8-bit unsigned integer Yes Specifies NetBIOS Node Type.
47 hex string of digits, in form of hex "digits", hex "digits", or 0xdigits Yes NetBIOS Scope.
48 One or more dotted quads Yes Specifies X Windows font server IP addresses.
49 One or more dotted quads Yes Specifies X Windows Display Manager.
50 None No Requested IP Address, used by client to indicate the address it wants.
51 32-bit unsigned integer Yes Lease time for the returned address. By default, the DHCP server uses the leasetimedefault keyword, but direct specification of option 51 overrides it.
52 None No Option overload. Client uses this to indicate the sname and file fields of the BOOTP packet may have options.
53 None No DHCP server or client uses this option to indicate the type of DHCP message.
54 None No DHCP server or client uses this option to indicate the server's address or the server to which the message is directed.
55 None No DHCP client uses this to indicate desired options.
56 An ASCII string Yes A string the DHCP server sends to the client. In general, this can be used by the DHCP server and client to indicate problems.
57 No No DHCP client uses this option to tell the DHCP server the maximum DHCP packet size the client can receive.
58 32-bit unsigned integer Yes Specifies the number of seconds until the client should send a renew packet.
59 32-bit unsigned integer Yes Specifies the number of seconds until the client should send a rebind packet.
60 None No DHCP client uses this option to indicate its vendor type. The DHCP server uses this field to match vendor containers.
61 None No DHCP client uses this to uniquely identify itself. The DHCP server uses this field to match client containers.
66 An ASCII string Yes Specifies the TFTP server name. This is a hostname and is used instead of the siaddr field if the client understands this option.
67 An ASCII string Yes Specifies the bootfile name. This can be used instead of the bootfile keyword, which places the file in the filename field of the packet.
68 One or more dotted quads, or NONE Yes Specifies addresses of home agents.
69 One or more dotted quads Yes Specifies default SMTP servers to use.
70 One or more dotted quads Yes Specifies default POP3 servers to use.
71 One or more dotted quads Yes Specifies default NNTP servers to use.
72 One or more dotted quads Yes Specifies default WWW servers to use.
73 One or more dotted quads Yes Specifies default Finger servers to use.
74 One or more dotted quads Yes Specifies default IRC servers to use.
75 One or more dotted quads Yes Specifies default Street Talk servers to use.
76 One or more dotted quads Yes Specifies default Street Talk directory assistance servers to use.
77 An ASCII string Yes The user site class identifier. The DHCP server uses this field to match class containers.
78 Mandatory Byte, one or more dotted quads Yes The SLP directory Agent Option specifies a list of IP addresses for Directory Agents
79 Mandatory Byte, and ASCII string Yes The ASCII string is a scope list, which is a comma delimited list, that indicates the scopes that an SLP Agent is configured to use
81 An ASCII string plus other items No The DHCP client uses this option to define the policy the DHCP server should use with respect to DDNS.
85 One or more dotted quads Yes NDS server option specifies one or more NDS servers for the client to contact for access to the DNS database. Servers should be listed in order of preference.
86 An ASCII string Yes NDS tree name option specifies the name of the NDS tree the client will be contacting.
87 An ASCII string Yes NDS context option specifies the initial NDS context the client should use.
93 None No The DHCP client uses this option to define the client system architecture.
94 None No The DHCP client uses this option to define the client network interface identifier.
117 One or more 16-bit unsigned integers Yes Name Service Search Option gives the preferred order of integer option code for name services. For example: 
Name Services              value
Domain Name Server Option  6
NIS Option                 41
118 One dotted quads No Subnet Selection Option is an option sent by the client asking the dhcp server to allocate the IP address from the specified subnet.
255 None No DHCP server and client use this option to indicate the end of an option list.