ARP Intenal Routing Issues....

If you have a computer system on your network that one minute you can ping then the next minute all the requests time out the this computer then you will probably have a crap router that cannot DNS updates or RIPv2 is not enabled.....
If you look closely then Windows will hold the answer, if you perform the command:


arp -a

You will see that it will return all the discovered devices on your network with their IP address and MAC address as shown below:


Interface: 192.168.0.6 --- 0x10003
Internet Address Physical Address Type
192.168.0.1 00-53-99-3b-2b-10 dynamic

192.168.0.2 00-gg-gg-03-gg-gg dynamic

However, if I have a problem with a server with the IP address of "192.168.0.12" if you ping this IP address you will notice that the first "Request Timed Out" response will take about 3-4 second(s)....why I hear you ask....well, as you ping a device Windows trys to obtain the MAC address for correct routing (IP-to-Physical)
So if you display the same command as above (arp -a) you will notice that you have a new entry in the translation table....


Interface: 192.168.0.6 --- 0x10003
Internet Address Physical Address Type
192.168.0.1 00-53-99-3b-2b-10 dynamic

192.168.0.2 00-gg-gg-03-gg-gg dynamic

192.168.0.12 00-00-00-00-00-00 invalid

This tells you that either Windows cannot get this information from the remote system of you have a malfunctioning device on the network.....what great news....
I got this exact problem, but I found if you ping your computer from the remote device all is OK for a short period then it cannot find the device again....
So if you get this error to resolve this add a static ARP entry for the remote computer with the IP address as shown below:


arp -s 192.168.0.12 00-01-02-03-04-05

Finally run the "arp -a" command again to see the new "static" entry....now you can always communicate with this device.....cool!


Interface: 192.168.0.6 --- 0x10003
Internet Address Physical Address Type
192.168.0.1 00-53-99-3b-2b-10 dynamic

192.168.0.2 00-gg-gg-03-gg-gg dynamic

192.168.0.12 00-01-02-03-04-05 static

You will now be able to continually communicate with this device....until you reboot and your ARP table gets refreshed, my advice...make a BAT or VBS file to add these entrys on startup!
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