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network-programmingethernetlanarp
Rugved Mahamune
Rugved Mahamune

Reputation: 566

What happens to ( system A) host's ARP table when another host (system B) leaves the network?

Every system in a network has its entry in the ARP table when a system leaves from the network what happens to its entry, if another system tries to send a packet how will it know it doesn't exist anymore. and how will the ARP table get updates?

Upvotes: 1

Views: 392

Answers (1)

Ron Maupin
Ron Maupin

Reputation: 6452

There is no reason for any host's ARP cache to have an entry for every other host on the layer-2 network. The ARP cache is populated by ARP requests and ARP replies. If you are referring to a host's or router's (a router is just another host on a layer-2 network) ARP cache, or switch's MAC address table, the entries will time out.

When a system leaves the layer-2 network, its entries in other hosts' ARP caches and the switches' MAC address tables will eventually time out. The other hosts don't know that the host has left the network, and the sending host will either attempt to send frames to the host which left the layer-2 network, or the sending host will send an ARP request for the MAC address of the host which left the network, depending on whether or not the entry is still in the ARP cache of the sending host. In either case, the attempt to send a packet will fail; in the first case the frame encapsulating the packet will be sent, and in the second case, the packet will be dropped by the sending host since it cannot be encapsulated in a frame because it doesn't have a MAC address which it can use to build the frame.

Upvotes: 2

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