Comments on: Host to Host through a Switch

By: Juan

Juan — Fri, 04 Oct 2024 18:55:41 +0000

In reply to Ed Harmoush. what i understand from all of this is that when Host1 send a message to Host2 once it hits the switch, the switch will flood an address resolution to everyone except the originator, that way when the host with the right Ip address receives this message it will send a message back (Ack) to the switch and this is when the switch takes the MAC Address and writes it down on the table "learning" a new MAC address for an IP address he already knew.

By: s. ponce

s. ponce — Tue, 02 Jul 2024 18:50:18 +0000

I was curious to ask, say there are two devices with different subnets both connected to a regular switch (not managed). if the switch only cares about the mac addresses, why couldn’t an application establish communication from one device to the other?. the switch knows the ports computer a and b are connected to, along with the mac address for each. does the application care about the ip addresses not being in the same subnet? or it depends on the the protocol use, maybe some protocols care, where others don’t. this is a question that has been haunting me for a while, I apologize if the intent of the question is not inherently clear, I don’t deal with networks much but I have run into this type of scenarios. thanks!

By: Karpurapu Rahul

Karpurapu Rahul — Sat, 10 Jul 2021 07:09:15 +0000

flooding will never be done when A wants to send to B. As we can see in the animation, the destination MAC was filled with that of the MAC address of B. How did A know the MAC address of B? A learnt it during the ARP protocol. So when B was sending its MAC address as a response to the ARP done by A, it had to go through the switch and then the switch would have learnt that the port on which b sits is 2. So there was no need for flooding to be done when A wants to send a message to B.

By: Ed Harmoush

Ed Harmoush — Mon, 07 Jun 2021 18:03:55 +0000

In reply to Jenny. You're welcome =). Yes, you are correct on both points.

By: Jenny

Jenny — Sat, 05 Jun 2021 12:22:15 +0000

Thank you Ed for your brilliant in-depth illumination of ARP process.

Just one thing, I wish to clarify : The switch has the job to do flooding for the broadcast frame, rather than to initiate the broadcast frame. Whereas the Host has the job to initiate the broadcast frame.

Now, after the ARP request got initiated, the host then placed the ARP request onto the connected wire(s), allowing its ethernet LINK to take care of the actual delivery of the broadcast frames. This means the cable wire(s) will deliver the ARP request to all DIRECTLY CONNECTED neighbours. Hope my interpretation of your article was on the right track. Many thanks !

By: Student

Student — Tue, 11 May 2021 17:03:50 +0000

Assume that the ARP tables of both devices (laptop and Raspberry) and the MAC address table of the switch are initially empty. Your laptop will now send 3 ping requests to the IP address of the Raspberries. Describe step by step,
which messages are sent from which host and where and when the information in the various tables is updated

By: Ed Harmoush

Ed Harmoush — Thu, 15 Apr 2021 17:37:28 +0000

In reply to nabilshazain. You're welcome =)

By: Ed Harmoush

Ed Harmoush — Thu, 15 Apr 2021 17:35:05 +0000

In reply to Anntria.

The hosts will still use IP addresses to speak to each other. The Switch, however, will never look into the L3 header to see the IP headers. See this for more info:

https://www.youtube.com/watch?v=gYN2qN11-wE

By: nabilshazain

nabilshazain — Sun, 11 Apr 2021 14:20:51 +0000

this is wonderful post.. Thank you dear Sir

By: Anntria

Anntria — Thu, 01 Apr 2021 06:50:16 +0000

How does 2 hosts communicate with each other with only a single switch in between.MAC addresses of both the hosts are given but IP address is not mentioned