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Last update: 2021-10-21

Appendix A – DHCP Options (RFC 2132)

A DHCP server can provide optional configurations to the client. Sophos Firewall provides support to configure following DHCP Options as defined in RFC 2132.

To set the options, refer to DHCP Management section.

Option Number Name Description Data Type
2 Time offset Time offset in seconds from UTC Four-byte numeric value
4 Time servers N/4 time server addresses Array of IP addresses
5 Name servers N/4 IEN-116 server addresses Array of IP addresses
7 Log servers N/4 logging server addresses Array of IP addresses
8 Cookie servers N/4 quote server addresses Array of IP addresses
9 LPR servers N/4 printer server addresses Array of IP addresses
10 Impress servers N/4 impress server addresses Array of IP addresses
11 RLP servers N/4 RLP server addresses Array of IP addresses
12 Host name Hostname string String
13 Boot file size Size of boot file in 512 byte chunks Two-byte numeric Value
14 Merit dump file Client to dump and name of file to dump to String
16 Swap server Swap server addresses IP address
17 Root path Path name for root disk String
18 Extension file Patch name for more BOOTP info String
19 IP layer forwarding Enable or disable IP forwarding Boolean
20 Src route enabler Enable or disable source routing Boolean
22 Maximum DG reassembly size Maximum datagram reassembly size Two-byte numeric value
23 Default IP TTL Default IP time-to-live One-byte numeric value
24 Path MTU aging timeout Path MTU aging timeout Four-byte numeric value
25 MTU plateau Path MTU plateau table Array of two-byte numeric values
26 Interface MTU Size Interface MTU size Two-byte numeric value
27 All subnets are local All subnets are local Boolean
28 Broadcast address Broadcast address IP address
29 Perform mask discovery Perform mask discovery Boolean
30 Provide mask to others Provide mask to others Boolean
31 Perform router discovery Perform router discovery Boolean
32 Router solicitation address Router solicitation address IP address
34 Trailer encapsulation Trailer encapsulation Boolean
35 ARP cache timeout ARP cache timeout Four-byte numeric value
36 Ethernet encapsulation Ethernet encapsulation Boolean
37 Default TCP TTL Default TCP TTL One-byte numeric value
38 TCP keepalive interval TCP keepalive interval Four-byte numeric value
39 TCP keepalive garbage TCP keepalive garbage Boolean
40 NIS domain name NIS domain name String
41 NIS server addresses NIS server addresses Array of IP addresses
42 NTP servers addresses NTP servers addresses Array of IP addresses
43 Vendor specific information Vendor specific information String
45 NetBIOS datagram distribution NetBIOS datagram distribution Array of IP addresses
46 NetBIOS node type NetBIOS node type One-byte numeric Value
47 NetBIOS scope NetBIOS scope String
48 X window font server X window font server Array of IP addresses
49 X window display manager X window display manager Array of IP addresses
50 Requested IP address Requested IP address IP addresses
51 IP address lease time IP address lease time Four-byte numeric value
52 Option overload Overload “sname” or “file” One-byte numeric value
53 DHCP message type DHCP message type One-byte numeric value
55 Parameter Request List Parameter request list Array of one-byte numeric values
56 Message DHCP error message String
57 DHCP maximum message size DHCP maximum message size Two-byte numeric value
58 Renew time value DHCP renewal (T1) time Four-byte numeric value
59 Rebinding time value DHCP rebinding (T2) time Four-byte numeric value
60 Client identifier Client identifier String
61 Client identifier Client identifier String
62 Netware/IP domain name Netware/IP domain name String
64 NIS+ V3 client domain name NIS+ V3 client domain name String
65 NIS+ V3 server address NIS+ V3 server address Array of IP addresses
66 TFTP server name TFTP server name String
67 Boot file name Boot file name String
68 Home agent addresses Home agent addresses Array of IP addresses
69 Simple mail server addresses Simple mail server addresses Array of IP addresses
70 Post office server addresses Post office server addresses Array of IP addresses
71 Network news server addresses Network news server addresses Array of IP addresses
72 WWW server addresses WWW server addresses Array of IP addresses
73 Finger server addresses Finger server addresses Array of IP addresses
74 Chat server addresses Chat server addresses Array of IP addresses
75 StreetTalk server addresses StreetTalk server addresses Array of IP addresses
76 StreetTalk directory assistance addresses StreetTalk directory assistance addresses Array of IP addresses
120 SIP server The SIP server DHCP option carries a 32-bit (binary) IPv4 address used by the SIP client to locate a SIP server. Array of IP addresses

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