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Operating modes and functions
ELSA MicroLink Cable
42
DHCP – 'on', 'off' or 'auto'?
The DHCP server in the devices of ELSA can be set to three different states:
'on': The DHCP server is permanently active. The configuration of the server (validity
of the address pool) is checked when this value is entered.
– When correctly configured, the device will be available to the network as a DHCP
server.
– In the event of an incorrect configuration (e.g. invalid pool limits), the DHCP
server is disabled and switches to the 'off' state.
'off': The DHCP server is permanently disabled.
'auto': The server is in automode. In this mode, after switching it on, the device
looks for other DHCP server within the local network.
– The device then disables its own DHCP server if any other DHCP servers are
found. This prevents the unconfigured router from assigning addresses not in the
local network when switched on.
– The device then enables its own DHCP server if on other DHCP servers are found.
Whether the server is active or not can be seen in the DHCP statistics.
The default state is 'auto'.
How are the addresses assigned?
IP address assignment
Before the DHCP server can assign IP addresses to the computers in the network, it first
needs to know which addresses are available for assignment. Three options exist for
determining the available selection of addresses:
The IP address can be taken from the address pool selected (start address pool to
end address pool). Any valid addresses in the local network can be entered here.
If '0.0.0.0' is entered instead, the DHCP server automatically determines the
addresses (start or end) from the LAN IP address settings in the 'TCP/IP module'.
If the cable modem has no LAN IP address of its own, the device will go into a
special operating mode. It then uses the IP address '10.0.0.254' for itself and the
address pool '10.x.x.x' for the assignment of IP addresses in the network. In this
state, the DHCP server only assigns IP addresses and their validity to the computers
in the network, but not the other information.
If only one computer in the network is booted and requests an IP address via DHCP with
its network settings, a device with an activated DHCP module will assign this computer
an address. A valid address is taken from the pool as an IP address. If the computer was
already assigned an IP address at some point in the past, it requests this same address