DHCP6LEASED.CONF(5) | File Formats Manual | DHCP6LEASED.CONF(5)

# NAME

`dhcp6leased.conf` — DHCPv6 client configuration file

# DESCRIPTION

The dhcp6leased(8) daemon is a dynamic host configuration protocol client daemon for IPv6 prefix delegation.

The `dhcp6leased.conf` config file is divided into the following main sections:

Macros
  Definitions of variables that can be used later, simplifying the configuration file.
Global configuration
  Global settings for dhcp6leased(8).
Prefix delegation
  dhcp6leased(8) requests prefix delegation from a DHCPv6 server and assigns prefixes to interfaces. This section defines on which interfaces prefix delegation should be requested and to which interfaces prefixes should be assigned.

## Macros

A macro is defined with a command of the form name=value. The macro name can contain letters, digits, and underscores and cannot be a reserved word (for example, `interface`). Within unquoted arguments, the string $name is later expanded to value.

## Global configuration

These settings affect the operation of the dhcp6leased(8) daemon as a whole.

`request rapid commit`
  Send the rapid commit DHCPv6 option, requesting a two-message exchange from the server instead of the normal four-message exchange.

## Prefix delegation

A list of interfaces on which to request prefix delegation:

`request prefix delegation on` name `for` {name[/prefix] ...}

This requests a prefix delegation on the upstream network interface name for the list of name[/prefix] network interfaces. If prefix is omitted a default of /64 is used.

dhcp6leased(8) will calculate the prefix length needed to cover all interfaces in the list. When a prefix is delegated by a DHCPv6 server, dhcp6leased(8) splits the prefix into smaller prefixes and assigns them to the interfaces in the order they are listed. This might create unassigned gaps in the delegated prefix.

For example if a /64 and /60 prefix are to be assigned to network interfaces, dhcp6leased(8) requests a /59 prefix. The prefix is then split into two /60 prefixes and the first /64 out of the first /60 prefix is assigned to the first interface. The second /60 prefix from the delegated /59 is assigned to the second interface. This leaves 15 unused /64 prefixes in the first /60.

Care should be taken to avoid renumbering of existing interfaces when new interfaces are added or existing interfaces are removed. New interfaces can be added to the end of the list or in places where unassigned gaps were present.

The special name `reserve` can be used to reserve space in the delegated prefix for later use or when an interface is removed.

Running dhcp6leased(8) in configtest mode with a verbosity of two or more will print the configuration file with comments indicated how prefixes would be assigned to network interfaces. This can be used to check that existing interface are not renumbered.

More than one prefix can be requested from a DHCPv6 server, however most ISP DHCPv6 servers will only delegate a single prefix. Therefore it is better to let dhcp6leased(8) request a single larger prefix and split it up. dhcp6leased(8) has a compile time limit on how many prefix requests per interface it can handle.

# FILES

/etc/dhcp6leased.conf
  dhcp6leased(8) configuration file.

# SEE ALSO

dhcp6leasectl(8), dhcp6leased(8)

July 8, 2025 | Debian