One of the most important lower layer protocols is known as ARP – the address resolution protocol. It’s an important protocol and one you’ll need some knowledge of in troubleshooting all sorts of network issues. From identifying latency problems to application issues affecting the network – it’s a useful to have some knowledge. It’s an essential part of learning to understand your network at the packet level and being able to spot abnormal traffic.
The issue you can have with troubleshooting any network is identifying what’s causing the problem and what devices are involved. For example if you’re investigating the network of a residential IP provider then you can focus on particular protocols and specific areas of the network. Invariably central proxies can be difficult to troubleshoot as most will carry (if not understand) all sorts of traffic and protocols. In addition the servers will be creating a communication channel between completely different devices and even networks.
Both logical and physical addresses are used for communication on a network. The use of logical addresses permits communication among multiple networks and indirectly connected devices. The use of physical addresses assists in communication on a singular network segment for devices that are directly linked to each other with a switch. These two types of addressing must work together in order for communication to occur.
Consider a situation where you want to interact with a device on your network. This device might be a server of some kind or simply one more work- station you need to share ﬁles with. The application you are actually using to initiate the communication is actually aware of the Internet Protocol address of the remote host (by means of DNS, addressed elsewhere), meaning the system ought to have all it needs to build the layer 3 through 7 information of the packet it wants to transmit.
The sole component of info it requires at this point is the layer 2 data link data consisting of the MAC address of the intended host. MAC addresses are actually required for the reason that a switch that interconnects devices on a network uses a Content Addressable Memory (CAM) table, which provides the MAC addresses of all of the devices connected into each one of its ports. When the switch receives traffic destined for a particular MAC address, it uses this table to know through which port to deliver the trafﬁc.
If the destination MAC address is unidentified, the broadcasting device will ﬁrst check for the address in its cache; in the event that it is not actually there, then this should be resolved by means of additional communicating on the network.
The resolution technique that TCP/IP networking (with IPv4) uses to resolve an IP address to a MAC address is called the Address Resolution Protocol (ARP), which is deﬁned in RFC 826. The ARP resolution process uses only two packets: an ARP request and an ARP response.