Configure interface `<interface>` with one or more interface addresses.

* **address** can be specified multiple times as IPv4 and/or IPv6 address,
  e.g. 192.0.2.1/24 and/or 2001:db8::1/64
* **dhcp** interface address is received by DHCP from a DHCP server on this
  segment.
* **dhcpv6** interface address is received by DHCPv6 from a DHCPv6 server on
  this segment.