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Contents

General options


Option 1 (Subnet Mask)

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.

Valid Values (Examples)

e.g. 255.255.0.0

Setting: netmask

Option 2 (Time Offset)

The time offset field specifies the offset of the client's subnet in seconds from Coordinated Universal Time (UTC).  The offset is expressed as a two's complement 32-bit integer.  A positive offset indicates a location east of the zero meridian and a negative offset indicates a location west of the zero meridian.

The table below gives the conversion of the different time zones around the world as specified in Option 2 of the DHCP RFC 2132.

UTC offset (in hour)

UTC offset in seconds

UTC offset in Hexadecimal

0

0

0000.0000

+1

3600

0000.0E10

+2

7200

0000.1C20

+3

10800

0000.2A30

+4

14400

0000.3840

+5

18000

0000.4650

+6

21600

0000.5460

+7

25200

0000.6270

+8

28800

0000.7080

+9

32400

0000.7E90

+10

36000

0000.8CA0

+11

39600

0000.9AB0

+12

43200

0000.A8C0

-1

-3600

FFFF.F1F0

-2

-7200

FFFF.E3E0

-3

-10800

FFFF.D5D0

-4

-14400

FFFF.C7C0

-5

-18000

FFFF.B9B0

-6

-21600

FFFF.ABA0

-7

-25200

FFFF.9D90

-8

-28800

FFFF.8F80

-9

-32400

FFFF.8170

-10

-36000

FFFF.7360

-11

-39600

FFFF.6550

The code for the time offset option is 2, and its length is 4 octets.

Valid Values (Examples)

UTC Offset : -7 hour
02:04:FF:FF:9D:90
UTC Offset : +7 hour
02:04:00:00:62:70

Option 3 (Router)

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.

Valid Values (Examples)

e.g. 192.168.0.1

Setting: gateway

Option 4 (Time Server)

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 (see also option 42 below).

This option is available since version 8.5.1

Valid Values (Examples)

e.g. 192.53.103.103 de.pool.ntp.org

Setting: ntp_server

Option 6 (DNS Server)

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.

Valid Values (Examples)

Private: 192.168.0.9 Public: 174.129.1.129

Setting: dns_server1 dns_server2

Option 12 (Hostname)

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.

Valid Values (Examples)

e.g. phone123

Setting: phone_name

Option 15 (DNS Domain)

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.

Valid Values (Examples)

e.g. company.com

Setting: dns_domain

Option 42 (NTP Server)

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.

Valid Values (Examples)

e.g. 192.53.103.103 de.pool.ntp.org

Setting: ntp_server

Option 50 (Requested IP Address)

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)

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)

This option is used to convey the type of the DHCP message. The code for this option is 53, and its length is 1. Valid 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)

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)

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 81 (Fully Qualified Domain Name)

Per default we don't send the DHCP option 81 because of RFC4702:

   The Host Name option [12], for
   example, contains an ASCII string representation of the client's host
   name.  In general, a client does not need to send redundant data, and
   therefore clients that send the Client FQDN option in their messages
   MUST NOT also send the Host Name option.

However, it is possible to send the option 81 (instead of option 12) via the setting dhcp_options_on_ip_aquire. In this case, the S-flag is set.

If both options are present, option 81 has the higher priority (and option 12 is no longer active). If no option is present then the 12 is used.

Option 120 (SIP Servers)

See RFC 3361

Valid Value (Example):  sip.company.com

Option 125 (Vendor-Identifying Vendor-Specific)

See RFC 3925. This option is used for tr69


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.

Valid Values: vlan id linux dhcpd3 syntax, for 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.

Valid Values: vlan qos linux dhcpd3 syntax, for example:

option vlan-qos code 133 = text ;
option vlan-qos "5"; 

Setting: vlan_qos



Auto-provisioning options


Option 43 (vendor-encapsulated-options)

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) sent 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). Values of options like 66/67/132/133, which are tunneled via option 43, take precedence over direct options 66/67/132/133.

Valid Values (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 - VCI)

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. snomD765) via this option to the DHCP server.

List of all Vendor class identifiers for Snom phones:

Desk phonesDECT base stationsConference & PA

snomD120

snomD305

snomD315

snomD335

snomD345

snomD375

snomD385

snom710

snom715

snomD717

snom725

snomD735

snomD745

snomD765

snomD785

snomM200SC

snomM300/xx.xx.xxxx

snomM700/xx.xx.xxxx

(xx.xx.xxxx being the firmware version, e.g. 04.10.0004)

snomC520

snomPA1

snomMP


Option 66 (TFTP server name)

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.

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

  1. tftp://...
  2. http://...
  3. https://...

Option 67 (Bootfile name)

This option is used to identify a configuration file 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.

  • Valid Values
    <path>
    e.g. settingfiles/snom/snom300.cfg, settingfiles/snom/snom320.htm, settingfiles/snom/snom360.xml
    <empty>
    or <not used> where <path> = path to the location of the setting file/script file
If only option 66 (server name) is specified and option 67 is empty or not specified, the phone will try to "guess" the configuration file name by creating this from its phone type and MAC address. The first file it tries to fetch is phoneType.htm, where phoneType is the same string as the vendor identifier which you can find in the table under 45633790. Apart from phoneType.htm, 3 additional files are tried as in the following example: if option 66 is set to "http://192.168.137.1", option 67 is not provided and the phone is a Snom715 with MAC address 0004137501E6, the phone will try to fetch the following files:
  • http://192.168.137.1/snom715.htm
  • http://192.168.137.1/snom715-0004137501E6.htm
  • http://192.168.137.1/snom715/snom715-firmware.htm
  • http://192.168.137.1/snom715-firmware.htm





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