We will show you what is the ARP protocol and what is it used for in computing. You will find all the information related to the how to use the Address Resolution Protocol and how it works in sending data packets on a network.
In addition, you will know the history and origin of the ARP protocol and why it was created, which will help you to know how the Inverse ARP and Reverse ARP variations.
We will also talk about advantages and disadvantages of Proxy ARP and the package structure Address Resolution Protocol. Don’t miss out on anything to become a true expert.
What is the ARP protocol?
To understand what the Address Resolution Protocol or ARP is, for its acronym in English, first you have to know what is the MAC address of a computer and what is the IP address. The first is a number of 48 bit divided into 6 groups and serves to identify a device in a network, that number is unique for the device and cannot change because it is related to your network card.
While the IP address It is an identifying number that a computer has within the network or the Internet. This address of 32 bits can change, if any adjustments are made. The problem arises when you want to relate both addresses of different extensions in one Red lan. For it, ARP protocol is used with which you can recognize the MAC of a node connected in the same network through its IP.
Keep in mind that when a device joins the network, the router or host gives you a unique IP to be identified. ARP is used for the other participants to interact with this new node. Thanks to the byte mapping and translation that this technology does, it is viable transmit data packets efficiently between those connected devices.
What is ARP for and how does it work?
When you connect a computer to a network, the new device needs to link with the other nodes to interact. Every time you want to send data packets between two computers, it is necessary for a hardware to act as a gateway, which requires validation to make the data flow to a specific host. For this, it is important to determine in advance whether or not that host belongs to the same local network, in which the new device is connected, or the hardware is included in a subnet.
After mapping and reviewing the subnet mask, it is determined whether or not the IP address in question belongs to a local network. If yes, that information is dumped into an ARP cache. This is done to optimize resources and save time. That cache is a limited list or table of MAC addresses, In which you can find dynamic and static entries, the latter being erased when the computer is turned off.
That is, if an IP address is in the cache, this address is used for redirection, but if it is not in the table, an ARP request is sent to all hosts on the network. In the latter case, an ARP request is sent with the recipient’s address in ARP broadcast form, FF: FF: FF: FF: FF: FF. The rest of the network participants compare this IP with their own addresses and if there is no match, they reject them.
When a device relates the address, it sends an ARP Reply where the MAC address is sent with the IP, leaving this information incorporated in the cache memory. Another way to use the Address Resolution Protocol it is when the destination host does not belong to the same subnet. So the sender of the data has to access a gateway through the combination of the IP and MAC bits so that the hardware resolves the data packets and the information is sent to the destination host.
If the recipient belongs to an adjacent subnet it is possible directly resolve the physical address. If the gateway is that of a remote subnet, the hardware address is resolved, but without the help of the aforementioned routing table. For what is necessary repeat the process as many times until the data reaches its destination or when the value 0 on the IP address header.
History and origin of the ARP protocol Why was it created?
The ARP protocol was born in the 1980s and was created to integrate the hardware addresses of the devices on a network with the Internet addresses and in this way to transmit data packets between the nodes. Thanks to its implementation, it is likely to solve the problem of to which device to deliver what is requested by the sender with the least possible effort.
ARP works at Layer 2 of the OSI model and its use is feasible in the networks of WiFi and on Ethernet, with which it is viable dynamically convert IP addresses and cache a couple of data from mapping to be used in the next order.
Inverse ARP and Reverse ARP What are they and how do they work?
The Inverse ARP or InARP function is a variation of the ARP protocol and consists of solving the IP addresses into MAC addresses. This system does not need to be a static configuration, which makes it more effective because it does not send requests, since it knows the IP addresses of the recipient or destination station. Through a complete message, it is possible to know if a circuit is active, where Inverse ARP It occurs every one minute by default to speed up the process.
However, Reverse ARP or RARP is a protocol that is applied when you want know an IP address of a hardware within the same network. To be able to use this system, it is necessary that the MAC addresses are configured in a central server, so that it can transfer the IP to the rest of the participants. At present this system was put aside, using the Dynamic Host Configuration Protocol or DHCP.
What is ARP proxy and what are the advantages and disadvantages of using it?
See below the advantages and disadvantages of using Proxy ARP:
Utility
To avoid routing or gateway hosts that are in remote subnets, technology is used ARP proxy with which a host responds to requests ARP to deliver the data packets.
Thanks to this protocol it is possible to make two hosts from different subnets connect without having to adjust changes to the devices that belong to the network. In this way, it is possible that when an ARP request arrives, it is the same host that works to respond, leaving aside the destination node. This can be done because it makes known the MAC with which it receives and transmits the data packets.
Proxy ARP is used in the following cases:
- When the router of a network disables Address Resolution.
- Every time a host does not have a default port configured.
- If a host has a improper network mask setting.
Advantages
Among the advantages that ARP Proxy has in the transmission of data packets within a network are:
- No need to use ARP Proxy technology on all routers, it only requires configuring a single router on the network.
- It is possible to use ARP Proxy when hosts do not have routing intelligence with a default gateway or gateway.
- The routing tables of the other hardware are not affected when this technology is used.
Disadvantages
The disadvantages of using Proxy ARP in a network are:
- Necessary use ARP tables Large size.
- If a network does not use Address Resolution Protocol, it will not be possible to use the technique ARP Proxy.
- It is possible to fall into spoofing. This means that security weakens because one host can easily replace the identity of another.
- ARP traffic increases considerably.
- It is vulnerable to denial of service or DoS attacks.
ARP Protocol Packet Structure
The ARP protocol packet structure is a message format where the parameters to be used are specified.
Take a look at the composition of this routing mechanism:
ARP packet generation
When you want to send a data packet to an IP, first the direction of the next jump that the data will have is determined. Then the hardware that should receive that packet is established. To consult the ARP module it is necessary to map the network, which must be Ethernet IEEE 802.3 or 4 or 5, it is done as the pair
The first thing the module is going to do is search your cache for IP address with mentioned mapping pair. If found, it returns the address of 48 bit and the process continues. Instead, if there isn’t, reject the sent data packet and create a network ARP broadcast.
ARP packet reception
Once the module gets a response from your IP cache lookup sends it to the host, which receives the ARP packet as a broadcast or as a peer-to-peer response. This causes the receiving device to pass the data packet to the ARP module and the requesting host receives a response. From all this it emerges that, the