As of firmware version LCOS 7.80, DHCP options make it possible to send not only an IP address to a DHCP client but additional information as well.
For a full list of DHCP options see RFC 2123 (http://www.ietf.org/rfc/rfc2132.txt).
1) In LANconfig, open the configuration dialog for the LANCOM router and navigate to the menu item Configuration -> TCP/IP -> DHCP -> DHCP options.
2) Click on the Add... button to create a new entry.
3) As specified in RFC 2132 section 3.8 (see below), a DHCP client can be notified of one or more DNS servers.
The information is structured as follows:
Option number = 6
Network name (as required)
Option type = IP address
Option value = e.g. 192.168.10.200 -> if just one DNS server is to be specified
Option value = e.g. 192.168.10.200,126.96.36.199 -> if multiple DNS servers are to be specified
Multiple values are separated by commas.
This enhanced system is unable to reproduce all of the possible options as some consist in part of an integer number and partly of character strings. This possibility is only available to those who can assemble the value byte-by-byte with the type "integer-8".
Other examples of options:
Time server IP address (NTP):
NetBIOS server address (NBNS):
There are also custom options that are manufacturer-dependent, as with the DHCP option 252 shown below.
Proxy server address:
- The option type for the 66 option must be string and the value must be the ip address of the tftp server.
Image-File for a PXE-Boot-Server:
Go to the menu IPv4 -> BootP -> stations and create a new entry which contains the MAC address of the PXE client (see figure below).