Ethernet Interface

The IP address for the ethernet network interface is assigned in several ways using the following modes:

• Dynamic Host Configuration
  This mode is mostly used. It requires a centralized DHCP server in the LAN network. DHCP server maintains a database of leased IP addresses, and assigns to the client an unused IP address. It specifies also a network mask and a default gateway to use, when the system wants to access the internet. The DHCP server specifies also a primary and optional secondary DNS server. The DNS server is used to resolve the IP address for a known host name. In order to use this mode, the option Dynamic Host Configuration must be enabled in the system configuration.
• AutoIP
  The system first tries the DHCP mode, and if it fails after a timeout of 60 seconds, the system starts an auto-configuration mode. It randomly selects an IP address and checks, if it is in use. If the chosen IP address is not used, the system starts using it. Otherwise the system tries a different random IP address. In this mode an IP address and network mask are assigned. The default gateway is not assigned, because it is not known. Connecting to internet is thus not possible from the AutoIP mode. The IP address is picked from the link-local IP address block (169.254.1.0 - 169.254.254.255). The network mask is 255.255.0.0.
• Static IP
  The IP address, network mask and default gateway are configured in the system configuration file. It is possible to change the IP address at runtime. The static configuration specifies also a primary and optional secondary DNS server.

Note

• In AutoIP mode, a DHCP client is still trying to obtain an IP address every 120 seconds. On success the IP address is re-assigned. The system then starts using a new, DHCP assigned IP address and the mode is changed back to DHCP mode. The AutoIP mode is an extension of the Dynamic Host Configuration mode.