Address Resolution Protocol - ARP

Address Resolution Protocol is a protocol that maps IP address to a mac address so hosts can be addressed. I want to make a video explaining ARP because it is starting to surface a lot in different videos that I’m making such as man in the middle, load balancing, and security.

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Hussein

[fujinafiul]

love your videos, to the point, well designed, cover the basics beautifully, thanks..!

[devprakash]

Wth . He explained it beautifully, I mean it was impeccable . My God !

[abdulmoizsheikh]

A bit confused about the ARP poisoning part. What happens when 2 nodes respond to an ARP request? How will the requester resolve these colliding responses?

[brod]

Is the MAC address also used by the router. does it need 44.2.2.2 (X) MAC address in order to send the packet to X.

[jjmayank]

At 03:00, you say we need mac to send frames. But do we ever send frames? Doesnt it always go to layer 1 ?

[truthadjustr]

Hi Hussein. If I can ssh into a server, how do I prove that it has been failed over? If the MAC, storage UUID all looks the same, then what else other way to know that I am now inside a failed-over instance?

[kamillatosinski]

If each request goes through the router, how can device no 5 pretend to be a router? Shouldn't router cut the chain first and immediately upon receiving the request say: "Hey, I'm the router", before forwarding the ARP request to other devices within the network?

[asimarunava]

6:07 i think layer 2 then Layer 3 and then Layer 7.

[ashutoshmishra]

Hey Hussein, thanks for the content you are providing. its awesome and i love the way you explaing things.

i have a doubt, when the client and server both are in the same public wifi network, request should first go to the router (because it'll follow star topology) and then router should broadcast this message in the network.
so basically in both the cases request frame will be same, IP will be destination server's IP (not router's IP) and MAC address will be Router's MAC address. and then in 1st case router will broadcast frame in internal network and in 2nd case router will broadcast frame in the outside network after replacing source IP and making entry in NAT table.

please correct me if i'm wrong..

[tekfreaks]

Hi Hussein. It was very informative. I have a question though. Do you need the MAC address of Google server to send the frame. If so, how will the gateway get the MAC address of Google server.

P.S. By your videos, I got to know, how to get the IP ADDRESS of Google. How about Mac address. Do we need MAC address ?

[nitishbhatia]

V Nice explanation.
Q1: How is ARP request made without knowing the mac address because osi layer requires mac address.
Q2: What if no machine in the lan responds back with mac address implying that ip address is no longer present in the lan. How long does machine wait for the response before it times out saying that mac address does not exist? Wouldn’t this be slow? Shouldn’t this be implemented the way service discovery works where new service/machine updates the router/gateway of its mac address and router/gateway becomes the source of truth for mac addresses in the lan?

[nmanikiran]

If we login to Google/ Gmail / Dropbox from different machine then they shoot a mail .

How can implement that or how can get the MAC address from where the request is coming from?

[amlivinginhell]

at 06:04, how did we get to know the mac address of the destination ip?

[nathanbenton]

Can a MAC address ever change for a single machine within a given network? By the way, there should be some kind of forum for your topics and subsequent discussions - like Reddit or something:D Thanks again for all your contributions and valuable, practical insight!

[harshgupta]

With google.com as the name in hand, how can the client even get the IP address of google.com at the very first place to decide that this IP address is not in it own subnet?

[kallikantzaros]

not even 1000 views in one year? What is wrong with YouTube