Do switches forward arp broadcasts???

[Mand0]

I have a question. In a simple switched enviroment, say 12 computers on a 12-port switch, if one of my nodes does not know the MAC address of the destination, but only its IP address. It will have to broadcast an arp request.

Now the question is, if the switch has the MAC address in its ARP table will it forward the broadcast to all the ports or will it respond to the node with the MAC in its table.

It seems to me that by the switch not responding, it creates unneccesary broadcasts, but it may also be that the switch uses its arp table for a completely different thing (switching.)

Anybody got any input on this???

 

[BuckWeet]

The switches ARP table is for its own personal use. For management interface reasons. If it was a layer 3 and above switch, the yes it has a publicly used ARP table per say. L2 switches only have MAC destination tables. Basically tables that tell it where that MAC is at. ARP's or any other kind of broadcast ethernet frame do get propagated throughout your network. This is the broadcast domain structure.

The best you can do is keep your broadcast domains small, 500 devices for IP, 300 for IPX, 200 for appletalk, etc.. is what they usually recommend. Now those numbers don't relate to any kind of NetBios or any other network applications. With those running, it might be wiser to go even smaller. Setup WINS, DNS, or any other kind of service that will help alleviate broadcasts..


BuckWeet