The reason for this is often due to use of an identical IP address for 2 devices having different MAC addresses within a short time. TCP/IP stations update a dynamically administered ARP table which
contains the assignments of IP-to-MAC addresses. If a replacement RFID Server which has the same IP address as its predecessor is placed in service, before resuming communication the "old" ARP entry device processing IP protocol before the RFID Server may need to be deleted.
ARP entries are automatically deleted after a certain time has passed with no data flow, so that if some considerable time has passed between when the device was replaced and resumption of communication, you can omit manual deletion. In addition, when restarted, the RFID Server generates special ARP packets which are used to update the ARP cache for newer TCP/IP stacks and switches.
Example 1: A Windows computer communicates with an RFID Server in the same IP subnet without use of a router. In this case you only need to use the following command to delete the no longer valid ARP entry: arp -d [IP address]
Example 2: Communication with an RFID Server takes place over one or more routers. After replacement, the ARP entry for the last router before the RFID Server (gateway) needs to be deleted. The specifics of this procedure can be found in the documentation from the respective manufacturer.
Note: Since switches also process and save the MAC addresses of the connected devices, these must also be taken into account when replacing a device.