Network+ Certification Exam Tutorial: ARP and Proxy ARP Explained

In yesterday& 39;s Network + tutorial, we talked about the importance of the Address Resolution Protocol (ARP) in today& 39;s networks. A host PC, the MAC and IP addresses from a remote host to send data to that remote host, and it is allowed, that ARP is the local host to the host to send remost the local host its MAC address with an ARP Request.

The ARP request is a broadcast-layer two, and like all L2 sends he has a target MAC address ff-ff-ff-ff-ff-ff. Switches us broadcasts, but routers are not, which is a fundamental problem. If it is a router between two computers, how can we possibly send an ARP request to the remote host, since routers do not forward broadcasts?

That where & 39; proxy ARP comes in. For this example, let us assume that on a host network segment connected RouterA & 39; s ethernet0 interface, host and is on a Network segment connected RouterA & 39; s ethernet1 interface. Host wants to send data to host, but not over host MAC address. An ARP request from the host will be sent to the router - but with proxy ARP, the router will actually respond to the ARP Request with the MAC address of the router interface, with the ARP request!

In this case RouterA response to the ARP Request with the MAC address of his own ethernet0 interface. This is transparent to the host - host sends data to host, the destination IP address, the host, but the MAC destination address will be that of RouterA & 39; s ethernet0 interface.

Since we have now discussed, ARP and proxy ARP, I would like to mention RARP - Reverse Address Resolution Protocol. RARP allows a host device, please send a request for its own IP address, and the answer will be answered by a RARP server. They do not see that more often RARP, DHCP, as does the same thing and much more, but you should know what makes RARP. And if you are not sure what DHCP works - not miss my next exam Network + tutorial! gisela evelyn



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