Cool Solution - Setting DHCP-Options

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Note: Cool Solutions are articles documenting additional functionality based on Univention products. Not all of the shown steps in the article are covered by Univention Support. For questions about your support coverage contact your contact person at Univention before you want to implement one of the shown steps.

Also regard the legal notes at Terms of Service.

Some systems, such as VOIP Phones or door keys require additional options as part of their DHCP Lease. These can be set via the UDM Commandline interface. The purpose of this article is to describe how to set these up in UCS.

Option Codes

The Entries in the DHCP configuration consist of two parts which are the triplet of option Name, Code and type and the actual value. The triplet is the same across all DHCP subnets and most, such as the time-servers pointer, are standardized and inbuilt into UCS. The value, however, can be different across the different subnets.

The option code triplet is set via UCR. It is recommended to use a global policy to ensure a consistent setting across all servers.

The variables are formed like


Let us the time-servers, ntp-servers and shoretel-handset options as an example. The time-servers and ntp-servers is a standard option and there is no need to define the code value. To set the vendor option for the ShoreTel VOIP phones on a single server issue the following commands:

ucr set dhcpd/options/shoretel-handset/156=string

Setting the Value

The value of the options is set via the LDAP. Currently, this is only possible from the command line. First, you need to find the subnet which you would like to change.

udm dhcp/dhcp list

The result will be a list of DHCP objects.

root@ucs-2788:~# udm dhcp/service list

DN: cn=univention.intranet,cn=dhcp,dc=univention,dc=intranet
ARG: None
  service: univention.intranet

We need the DN to modify the object and set the options with the following command

udm dhcp/service modify --dn '<DN of the service>' --append option='time-servers <IP UCS-Master>' \ 
--append option='ntp-servers <IP UCS-Master>' --append option='shoretel-handset "<config>"'

Please pay attention to the quoting. The DHCP configuration requires strings, like for the ShoreTel config, to be enclosed in ". In my example, this would result in the following command

udm dhcp/service modify --dn 'cn=univention.intranet,cn=dhcp,dc=univention,dc=intranet' --append option='time-servers' \ 
--append option='ntp-servers' --append option='shoretel-handset "ftpservers=,country=1,language=1,layer2tagging=1,vlanid=2"'

Please be aware that the time-servers and ntp-servers variables should be set to a UCS Domain Controller, to ensure Kerberos is working correctly.

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