The Automatic NCP is a system-defined profile that is made up of one link NCU and one interface NCU for each physical link that is present in the system. The NCU activation policy in this NCP is to prefer connected, wired links over wireless links and to plumb both IPv4 and IPv6 on each enabled link. DHCP is used to obtain IPv4 addresses. Stateless Autoconf and DHCP are used to obtain IPv6 addresses. The Automatic NCP changes dynamically when new links are inserted or removed from the system. All NCUs that correspond to the inserted or removed link are also added or removed at the same time. The profile is updated automatically by the nwamd daemon.
When active, the Automatic NCP implements the following basic policy:
Configure all available (connected) Ethernet interfaces by using DHCP.
If no Ethernet interfaces are connected, or if none can obtain an IP address, enable one wireless interface, automatically connecting to the best available WLAN from the Known WLAN list. See Description of a Known WLAN.
Until at least one IP4 address has been obtained, keep the NoNet Location active. See Description of a Location Profile. This Location provides a strict set of IP Filter rules that only pass data that is relevant to IP address acquisition (DHCP and IPv6 autoconf messages). All of the properties of the NoNet Location, with the exception of the activation conditions, can be modified.
When at least one IP address has been assigned to one of the system's interfaces, activate the Automatic Location. This Location has no IP Filter or IPsec rules. The Location applies the domain name system (DNS) configuration data that is obtained from the DHCP server. As with the NoNet Location, all of the properties of the Automatic Location, with the exception of its activation conditions, can be modified.
You can optionally configure user-defined NCPs. You must explicitly add and remove NCUs from the specified NCP. You can also create NCUs that do not correlate to any link that is currently present in the system. In addition, you can determine the policy for the user-defined NCP. For example, you can allow multiple links and interfaces to be enabled on the system at a given time, as well as specify different dependency relationships between NCUs and static IP addresses.