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I have a question that my ubuntu's arp table always has one device (router) except I ping other devices, the arp table will be update. But I don't know what the mechanism of arp table updating. Could someone explain the mechanism? Thank you.

Babau_Ho
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1 Answers1

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I am not sure about the detailed mechanism, but I assume you have the router configured as the gateway.

This will set the default route to this gateway and it is most likely this makes an ARP request to see if the gateway is there (most likely the route command during interface setup)

Hayt
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  • Sorry for my typo. I meant why my arp table has no other device, even if other device exist in the LAN. – Babau_Ho Aug 31 '16 at 14:32
  • Do they have a gateway? The gateway should be in the arp table by default and all others inside the network only when once contacted in any way – Hayt Aug 31 '16 at 14:35
  • I meant that my arp table contain gateway information only, but I expect to see other device. Thank you. – Babau_Ho Aug 31 '16 at 14:45
  • Are they there after you pinged other devices? and this also applies only for other devices in your subnet. When you want to reach a device outside of your subnet it goes over the gateway so you don't get an arp entry. For more detailed networking information you should ask http://serverfault.com/ though – Hayt Aug 31 '16 at 14:47
  • If I ping other device, arp table will be updated. But I don't want to do it. – Babau_Ho Aug 31 '16 at 14:56