Assign an IP address to an Ethernet reader
You can assign a reader a static IP address or a dynamic IP address via DHCP. In maintenance mode, you can also assign a link-local IP address. Upon power-up or changes to the Ethernet connection, the reader will directly start to check for an address in that order.
Static IP address
The reader first checks for a static IP address in its configuration. If you want to assign static IP addresses, you can only have 1 reader per subnet, and readers must be isolated by NAT routers.
To configure a static IP address:
- In the Ethernet host interface component, enable the option Use Static IP Address Instead of DHCP.
- Specify IP address, netmask, default gateway, and DNS server.
With this configuration, the reader will probe the assigned IP address using ARP. If the address is unique, the reader adopts it. Otherwise, the reader indicates an address conflict with 4 red blinks.
Deploy configuration before reader installation
While you can usually deploy the reader configuration after installation, you'll need to deploy it before installation in this case.
If no static IP address is configured, the reader enables its DHCP client to obtain an IP address dynamically. In maintenance mode, the DHCP client is always enabled.
The reader starts to poll for a DCHP server.
The interval between 2 polls starts at 1 second and doubles with every request to a max. interval of 60 seconds.
Once a DHCP server is found, polling stops.
The reader receives an IP address and other network parameters, i.e. netmask, default gateway, and DNS server.
If the reader has been assigned an IP address before, it tries to obtain the same address again.
However, it's up to the DHCP server to acknowledge this request or to assign a new address.
The reader probes the IP address using ARP.
If the address is unique, the reader adopts the assigned network configuration. Otherwise, the reader indicates an address conflict with 4 red blinks.
The address is used until the lease expires. Renewal starts after half of the lease duration.
For more details on the implementation, see RFC2131.
If neither a static nor a DHCP IP address is available, the reader obtains a link-local IP address.
Only enabled in maintenance mode
Link-local is only relevant if no other addressing mechanism is available. Typically, that's the case in maintenance mode when you directly connect the reader to a maintenance laptop without a DHCP server.
- The reader selects a random address within the reserved address block 169.254.0.0/16.
- The reader probes the IP address using ARP.
- If the reader receives a reply indicating that this address is already in use, it chooses a new random address and repeats from step 1.
This process may take several seconds.
For more details on the implementation, see RFC3927.
The default procedure for productive use is to assign 1 IP address to each reader (i.e. a static or a DHCP address). However, it's possible to assign both a static and a DHCP IP address via the reader configuration (check back with us for details if needed).
The reader will then use the addresses as follows:
- Incoming connections: The reader responds with the IP address via which it was addressed.
- Outgoing connections: The reader uses the IP address which is in the same subnet as the remote IP address. If this applies to none of the available addresses, the reader uses the static IP address as first and the DHCP IP address as second preference.