DHCP Options

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我是靠谱客的博主时尚小懒虫，最近开发中收集的这篇文章主要介绍DHCP Options，觉得挺不错的，现在分享给大家，希望可以做个参考。

概述

General Options

Option 1 (Subnet Mask)

Description

The subnet mask option specifies the client's subnet mask as per RFC 950. If both the subnet mask and the router option are specified in a DHCP reply, the subnet mask option MUST be first. The code for the subnet mask option is 1, and its length is 4 octets.

VALIDVALUE

e.g. 255.255.0.0

SETTING

netmask

Option 3 (Router)

Description

The router option specifies a list of IP addresses for routers on the client's subnet. Routers SHOULD be listed in order of preference. The code for the router option is 3. The minimum length for the router option is 4 octets, and the length MUST always be a multiple of 4.

VALIDVALUE

e.g. 192.168.0.1

SETTING

gateway

Option 4 (Time Server)

Description

The time server option specifies the time server (RFC 868), available to the client. The code for the time server option is 4. The minimum length for this option is 4 octets, and the length MUST always be a multiple of 4. Time Server is mapped to NTP Server.

Available since 8.5.1

VALIDVALUE

192.53.103.103, de.pool.ntp.org

SETTING

ntp_server

Option 6 (DNS Server)

Description

The domain name server option specifies a list of Domain Name System (STD 13, RFC 1035) name servers available to the client. Servers SHOULD be listed in order of preference. The code for the domain name server option is 6. The minimum length for this option is 4 octets, and the length MUST always be a multiple of 4.

VALIDVALUE

Private: 192.168.0.9

Public: 174.129.1.129

SETTING

dns_server1

dns_server2

Option 12 (Hostname)

Description

This option specifies the name of the client. The name may or may not be qualified with the local domain name (see section 3.17 for the preferred way to retrieve the domain name). See RFC 1035 for character set restrictions. The code for this option is 12, and its minimum length is 1.

VALIDVALUE

phone123

SETTING

phone_name

Option 15 (DNS Domain)

Description

This option specifies the domain name that client should use when resolving hostnames via the Domain Name System. The code for this option is 15. Its minimum length is 1.

VALIDVALUE

company.com

SETTING

dns_domain

Option 42 (NTP Server)

Description

The NTP server option specifies the NTP server (RFC 868), available to the client. The code for the NTP server option is 42. The minimum length for this option is 4 octets, and the length MUST always be a multiple of 4.

VALIDVALUE

192.53.103.103, de.pool.ntp.org

SETTING

ntp_server

Option 50 (Requested IP Address)

Description

This option is used in a client request (DHCPDISCOVER) to allow the client to request that a particular IP address be assigned. The code for this option is 50, and its length is 4.

Option 51 (IP Address Lease Time)

Description

This option is used in a client request (DHCPDISCOVER or DHCPREQUEST) to allow the client to request a lease time for the IP address. In a server reply (DHCPOFFER), a DHCP server uses this option to specify the lease time it is willing to offer. The time is in units of seconds, and is specified as a 32-bit unsigned integer. The code for this option is 51, and its length is 4.

Option 53 (DHCP Message Type)

Description

This option is used to convey the type of the DHCP message. The code for this option is 53, and its length is 1. Legal values for this option are:

1. DHCPDISCOVER

2. DHCPOFFER

3. DHCPREQUEST

4. DHCPDECLINE

5. DHCPACK

6. DHCPNAK

7. DHCPRELEASE

8. DHCPINFORM

Option 54 (Server Identifier)

Description

This option is used in DHCPOFFER and DHCPREQUEST messages, and may optionally be included in the DHCPACK and DHCPNAK messages. DHCP servers include this option in the DHCPOFFER in order to allow the client to distinguish between lease offers. DHCP clients use the contents of the 'server identifier' field as the destination address for any DHCP messages unicast to the DHCP server. DHCP clients also indicate which of several lease offers is being accepted by including this option in a DHCPREQUEST message. The identifier is the IP address of the selected server. The code for this option is 54, and its length is 4.

Option 55 (Parameter Request List)

Description

This option is used by a DHCP client to request values for specified configuration parameters. The list of requested parameters is

specified as n octets, where each octet is a valid DHCP option code as defined in this document. The client MAY list the options in order of preference. The DHCP server is not required to return the options in the requested order, but MUST try to insert the requested options in the order requested by the client. The code for this option is 55. Its minimum length is 1.

Option 120 (SIP Servers)

Description

RFC 3361

VALIDVALUE

e.g. sip.company.com

Option 125 (Vendor-Identifying Vendor-Specific)

Description

RFC 3925

VALIDVALUE

e.g.

Option 135 (HTTP Proxy for phone-specific applications)

Description

RFC 4578

VALIDVALUE

Option 143 ()

Description

RFC 3942

VALIDVALUE

VLAN Options

Option 132 (vlan-id)

Description

Read more about vlan tagging and vlan id here: IEEE802.1Q.

supported since 7.3.24/8.2.7.

VALIDVALUE

vlan id

linux dhcpd3 syntax example:

option vlan-id code 132 = text ;

option vlan-id "128";

SETTING

vlan_id

Option 133 (vlan-qos)

Description

Here you can read more about vlan tagging IEEE802.1Q and vlan qos IEEE802.1P.

supported since 7.3.24/8.2.7.

VALIDVALUE

linux dhcpd3 syntax example:

option vlan-qos code 133 = text ;

option vlan-qos "5";

SETTING

vlan_qos

Auto Provisioning Options

Option 43 (vendor-encapsulated-options)

Firmware

Encapsulated Option 66 and Option 67 are supported since 7.3.17/8.2.1

Encapsulated Option 132 and Option 133 are supported since 7.3.24/8.2.7.

Description

Encapsulated DHCP options, for encoding see RFC 2132 Section 2. DHCP Option Field Format; One can tunnel vendor specific DHCP options depending on the vendor-id (option 60) send before from the phone to the DHCP server. Vendor specific DHCP options may be provided encapsulated in option 43, see RFC 2132 Section 8.4. Vendor Specific Information.

VALIDVALUE (Examples)

linux dhcpd3 syntax:

option vendor-encapsulated-options

42:0c:68:74:74:70:3a:2f:2f:74:65:73:74:00:43:12:73:6e:6f:6d:2f:73:65:74:74:69:6e:67:73:2e:70:68:70:00;

Which means tunnel opt 66 http://test and opt 67 snom/settings.php via opt 43.

option vendor-encapsulated-options

84:02:33:00;

Which means tunnel opt 132 value 3 via opt 43.

option vendor-encapsulated-options

84:04:31:31:34:00:85:02:35:00;

Which means tunnel opt 132 value 114 and opt 133 value 5 via opt 43.

Option 60 (Vendor class identifier)

Firmware

Supported since 7.3.15

Description

This option is used by DHCP clients to optionally identify the vendor type and configuration of a DHCP client. The information is a string of n octets, interpreted by servers. Vendors may choose to define specific vendor class identifiers to convey particular configuration or other identification information about a client. For example, the identifier may encode the client's hardware configuration. Servers not equipped to interpret the class-specific information sent by a client MUST ignore it (although it may be reported). Servers that respond SHOULD only use option 43 to return the vendor-specific information to the client. The code for this option is 60, and its minimum length is 1.

The phone sends its type (i.e. snom320) via this option to the DHCP server.

Option 66 (TFTP server name)

Description

This option is used to identify a TFTP server when the 'sname' field in the DHCP header has been used for DHCP options. The code for this option is 66, and its minimum length is 1.

VALIDVALUE

<protocol> : // <IP address> or <domain> e.g. http://10.0.0.2, https://provisioning.company.com

<IP address> or <domain> e.g. 10.0.0.2, provisioning.company.com

where <protocol> = server type/protocol

where <IP address> = server IP address

where <domain> = server domain name

NOTE

Without specifying the <protocol> the firmware will attempt all supported server protocol types consecutively:

1. tftp://...

2. http://...

3. https://...

SETTING

update_server

Option 67 (Bootfile name)

Description

This option is used to identify a bootfile when the 'file' field in the DHCP header has been used for DHCP options. The code for this option is 67, and its minimum length is 1.

VALIDVALUE

<path> e.g. settingfiles/snom/snom300.cfg, settingfiles/snom/snom320.htm, settingfiles/snom/snom360.xml

where <path> = path to the location of the setting file/script file

NOTE

If this option is empty or not specified at all the firmware automatically requests the following setting files, except the whole URL is encoded in option 66:

all snom300 phones request --> http://<domain>/snom300.htm

all snom320 phones request --> http://<domain>/snom320.htm

all snom360 phones request --> http://<domain>/snom360.htm

all snom370 phones request --> http://<domain>/snom370.htm

all snom820 phones request --> http://<domain>/snom820.htm

all snom870 phones request --> http://<domain>/snom870.htm

all snom MeetingPoint phones request --> http://<domain>/snommp.htm

SETTING