130 • Fieldbus CommunicationETHERNETWAGO-I/O-SYSTEM 750PROFINET IO4.1.3.4.3 DHCP (Dynamic Host Configuration Protocol)The coupler’s/controller’s built-in HTML pages provide an option for IPconfiguration from a DHCP server, a BootP server, or the data stored in itsEEPROM by default.NoteThe network configuration via DHCP is not stored in the EEPROM, this onlyoccurs when using the BootP protocol.The DHCP client allows dynamic network configuration of thecoupler/controller by setting the following parameters:Parameter MeaningIP address of the client Network address of the coupler/controllerIP address of therouterIf communication is to take place outside of the local network,the IP address of the routers (gateway) is indicated in thisparameter.Subnet mask The Subnet mask makes the coupler/controller able todifferentiate, which parts of the IP address determine thenetwork and which the network station.IP addresses of theDNS serversHere the IP addresses can be entered by maximally 2 DNSservers.Lease time Here the maximum duration can be defined, how long thecoupler/controller keeps the assigned IP address. The maximumlease time is 24.8 days. This results from the internal resolutionof timer.Renewing time The Renewing time indicates, starting from when thecoupler/controller must worry about the renewal of the leasingtime.Rebinding time The Rebinding time indicates, after which time thecoupler/controller must have gotten its new address.In the case of configuration of network parameters via the DHCP protocol, thecoupler/controller automatically sends a request to a DHCP server afterinitialisation. If there is no response, the request is sent again after 4 seconds,a further one after 8 seconds and again after 16 seconds. If all requests remainunanswered, a blink code is output via the “IO” LED. Transfer of theparameters from the EEPROM is not possible.Where a lease time is used, the values for the renewing and rebinding timemust also be specified. After the renewing time expires, the coupler/controllerattempts to automatically renew the lease time for its IP address . If thiscontinually fails up to the rebinding time, the coupler/controller attempts toobtain a new IP address. The time for the renewing should be about one halfof the lease time. The rebinding time should be about 7 / 8 of the lease time.
