table which contains the associations of IP addresses to MAC addresses. If a replacement Web Thermometer is taken into operation with the same IP address as its predecessor, then prior to reestablishing communication, it may therefore be necessary (if appropriate) to delete the "old" ARP entry in the last device evaluating the IP protocol before the Web thermometer.
After a certain time, ARP entries are deleted automatically with no data flow, so that, if a longer interval elapses between device replacement and the reestablishment of communications, it is possible to do without the manual deletion. Above and beyond that, when restarting, the Web Thermometer generates special ARP packages which have the function of updating the ARP cache of newer TCP/IP stacks and switches.
Example 1: A Windows computer communicates with a Web Thermometer in the same IP sub-network without using a router. In this case, it is sufficient to delete the no longer valid ARP entry using the following command: arp -d [IP address]
Example 2: Communication with a Web thermometer runs via one or more routers. After a replacement, the ARP entry of the last router (gateway) situated before the Web Thermometer must be deleted. The specific procedure can be found in the documentation of the relevant 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.
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