Network list

DHCP settings for the IP networks are defined in this table.

• Network name The name of the network which the DHCP server settings apply to.
• DHCP server enabled DHCP server operating mode in this network. Depending on the operating mode, the DHCP server can enable or disable itself. You can see whether the DHCP server is enabled from the DHCP statistics. Possible values:
  • No: DHCP server is permanently switched off.
  • Automatic: With this setting, the device regularly searches the local network for other DHCP servers. The LAN-Rx/Tx LED flashes briefly when this search is in progress.
  If another DHCP server is discovered the device switches its own DHCP server off. If the LANCOM Router is not configured with an IP address, then it switches into DHCP client mode and queries the LAN DHCP server for an IP address. This prevents unconfigured devices introduced to the network from assigning addresses unintentionally. If no other DHCP server is discovered the device switches its own DHCP server on. If another DHCP server is activated later, then the DHCP server in the LANCOM Router will be disabled.
  • 'Yes': DHCP server is permanently switched on. When this value is entered the server configuration (validity of the address pool) is checked.
  If the configuration is correct then the device starts operating as a DHCP server in the network. Errors in the configuration (e.g. invalid pool limits) will cause the DHCP server to be deactivated.
  • 'Client mode': The DHCP server is disabled, the device behaves as a DHCP client and obtains its address from another DHCP server in the LAN.
  • 'Relay requests': The DHCP server is active and receives requests from DHCP clients in the LAN. The device does not respond to requests, but forwards them to a central DHCP server elsewhere in the network (DHCP relay agent mode).
  Default:
  • Automatic
  Note: Only use the setting "Yes" if you are certain that no other DHCP server is active in the LAN.
  Note: Only use the "client mode" setting if you are certain that another DHCP server is in the LAN and actively assigning IP addresses.
• Broadcast bit check This setting decides whether the broadcast bit from clients is to be checked. If the bit is not checked then all DHCP messages are sent as broadcasts.
• Start address The first IP address in the pool available to the clients. If no address is entered here the DHCP takes the first available IP address from the network (as determined by network address and netmask).
• End address The last IP address in the pool available to the clients. If no address is entered here the DHCP takes the last available IP address from the network (as determined by network address and netmask).
• Network mask Corresponding netmask for the address pool available to the clients. If no address is entered here the DHCP server uses the netmask from the corresponding network.
• Broadcast As a rule, broadcast packets in a local network have an address which results from the valid IP addresses and the netmask. In special cases (e.g. when using subnets for a selection of workstations) it may be necessary to use a different broadcast address. In this case the broadcast address is entered into the DHCP module.
  Note: We recommend that only experienced network specialists change the pre-setting for the broadcast address. Errors in the configuration here can lead to costly connections being established!
• Standard gateway As standard, the LANCOM issues its own IP address as the gateway address to computers making requests. If necessary, the IP address of another gateway can be transmitted if a corresponding address is entered here.
• DNS default IP address of the DNS name server for the forwarding of DNS requests.
• DNS backup IP address of the backup DNS name server for the forwarding of DNS requests, in the event that the first name server fails.
• NBNS default IP address of the NetBIOS name server for the forwarding of NetBIOS requests.
• NBNS backup IP address of the backup NBNS name server for the forwarding of NBNS requests, in the event that the first name server fails.
• Server address This is where the IP address for the superordinate DHCP server is entered when the mode 'Relay requests' is selected.
• Caching of server responses This option allows the responses from the superordinate DHCP server to be stored in the LANCOM Router. Subsequent requests can then be answered by the LANCOM Router itself. This option is useful if the superordinate DHCP server can only be reached via a connection which incurs costs.
• Adapting server responses to the local network This option allows the responses from the superordinate DHCP server to be adapted to the local network. When activated, the LANCOM adapts the responses from the superordinate DHCP server by replacing the following entries with its own address (or locally configured addresses):
  • Gateway
  • Network mask
  • Broadcast address
  • DNS server
  • NBNS server
  • Server ID
  This option is worthwhile if the superordinate DHCP server does not permit the separate configuration for DHCP clients in another network.