Does HUBS use ip addresses?

I know it might sound dumb this question guys but as I'm studying with a couple of friends this question came to discussion, one of the guys stated that he went to a premise where his client had only a hub no router in between just the hub connecting several computers lets say 7 with static ip address assign, only 3 of them had the same ip address manually assign he was getting a pop up windows saying that there was a conflict of ip address i would say,

don't hubs and switches go by mac addresses ???

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blackninja

Hubs and switches operate at layer 2 but the computer still needs a layer 3 address to talk to other computers.

So on 7 computers on a hub, they would need 7 different IP addresses,which are in the same subnet.

Computer A transmitting to B would broadcast the frames to every port (except the one it came out of) and on the port computer B is attached will be the only one to accept the frames.

Learn about ARP.

fly351

No they do not. Hub's operate at layer 1. They are just a multi-port repeater. Switches operate at layer 2 which forward/filter based on the hardware address (eq MAC address).

blackninja

fly351 wrote: »

No they do not. Hub's operate at layer 1. They are just a multi-port repeater. Switches operate at layer 2 which forward/filter based on the hardware address (eq MAC address).

Ohh.....my bad. Tired.

But I'm sure you knew what I meant, just a little boo boo.

fly351

lol yah I do. My post probably sounds as if it is directed to you but I actually was typing it before you replied

E1or0

I know that hubs operates at layer 1

now the tricky question something i cant still understand is if hubs forward every frame to every port and only the destination host will accept the frame base on its mac address, why does every host still need an ip address in order to comunicate? since hubs are not layer 3 devices

networker050184

The hub doesn't operate at L3 but the host does. Think of how a host gets data to another. It first needs the destination IP address (via DNS, manually telling it etc.). Then it uses arp to get the L2 address. If it didn't have a destination IP address how could it arp for the other ends MAC?

Paul Boz

Think of computers as layer 3 devices. Because computers speak in terms of IP addresses ARP exists to translate layer 3 IP addresses to layer 2 MAC addresses. Computers may need to be globally accessible so IP addressing is a must. As others have said, hubs don't use IP or MAC addresses. They just mirror everything from every port to all other ports.

Think of it this way. A computer can't just say "hey I want to send this data over to that computer over there." It has to be more specific by specifying an address.

E1or0

Networker that explanation makes perfect sence, there is not way for arp to get a mac address of a device without that device having an ip address assign - now i get it

blackninja
fly
networker
pauk - very good as well, i always see computers as layer 3 devices

thank you all for your time

fly351

E1or0 wrote: »

very good as well, i always see computers as layer 3 devices

Just remember... computers operate on all layers

dynamik

fly351 wrote: »

Just remember... computers operate on all layers

Yea, I was going to say, Paul's computer must suck. I use an L7 computer that has applications.

(We actually just gave him an old Linksys switch with a Fischer-Price front-end. It's been keeping him busy for hours.)

E1or0

Think of computers as layer 3 devices. Because computers speak in terms of IP addresses ARP exists to translate layer 3 IP addresses to layer 2 MAC addresses. Computers may need to be globally accessible so IP addressing is a must. As others have said, hubs don't use IP or MAC addresses. They just mirror everything from every port to all other ports.

Think of it this way. A computer can't just say "hey I want to send this data over to that computer over there." It has to be more specific by specifying an address.

They just mirror everything from every port to all other ports.
Quick question that came to my attention just about now, does hubs use ARP in order to get a mac address of a host? I always thought only switches can do this

dynamik

Hubs do not. They're layer-1 and just repeat electrical signals.

phantasm

E1or0 wrote: »

They just mirror everything from every port to all other ports.
Quick question that came to my attention just about now, do hubs use ARP in order to get a mac address of a host? I always thought only switches can do this

Ok, after that correction I would suggest you read up on ARP and RARP.

billscott92787

Just think of a HUB as a multi-port repeater. It's job is to clean up a signal and send it back out on the physical medium. Why would you do this? Normally you don't see them used too much anymore it's mainly switches you see used for the most part. But, say you have a distance that exceeds the specifications of your medium, you could implement the hub to connect your medium, then have medium going out the other side, to "extend" the length of your path. Make sense?

That's all a hub does. Remember as well, if you are using a hub, all connected device use shared medium, since all devices that are connected are in the same collision domain, unlike a switch, where each device is in its' own collision domain and has it's own bandwidth. What I mean for example,

E1or0

Originally posted by Networker

The hub doesn't operate at L3 but the host does. Think of how a host gets data to another. It first needs the destination IP address (via DNS, manually telling it etc.). Then it uses arp to get the L2 address. If it didn't have a destination IP address how could it arp for the other ends MAC?

Originally posted by Dinamik

Hubs do not. They're layer-1 and just repeat electrical signals.

It seems like some of you guys have doubs about the question wether hubs use ARP or not, if Hubs don't use ARP every host connected to the HUB wont neccesaryly need an ip addresses assign correct ?

Me personally I don't think hubs use ARP to get to a host, a hub is just a repeater the Host is the one building the frame with its source and destination mac address, that frame will eventually get to its destination once it arrive at the designated host, there is no need for ip address to be involve

I think the only reason that hosts connected to a hub uses ip addresses is so that group of hosts can be found under a specific subnet or if they are connected to a switch Am I wrong or right?

I'm still a noob on this guys have patience with me

Thank you

networker050184

Dude, forget ARP and hub in the same sentence

. A hub simply regenerates the incoming electrical signal and sends it out all the other ports. It doesn't care what that signal is.

alan2308

E1or0 wrote: »

It seems like some of you guys have doubs about the question wether hubs use ARP or not, if Hubs don't use ARP every host connected to the HUB wont neccesaryly need an ip addresses assign correct ?

Hubs don't "use" anything, they just regenerate the signal and send it back out every other port, as networker already stated. Hubs exist at layer 1, and IP addresses exist at layer 3 so an IP address would have no meaning or purpose for the hub.

The application (be it arp or anything else) is completely ignorant of whether the network is using a hub, a switch, or not even using Ethernet at all. Arp maps an IP address (layer 3) with a MAC address (layer 2), so like IP addresses, ARP has no use in a hub's world.

I think what you need at this point is a little more reading of the OSI and TCP/IP models. A better understanding of the layers and how they interact will clear this all up for you.

E1or0

Networker I understand how Hubs and Switches work back to the main question, why 3 out of 7 computers connected to a hub with the same ip address assign, manually assign can give you a conflict when a hub is not even a layer 3 device, its layer 1 and does not use arp.

why 3 computers that connects to the same hub cannot communicate do to the fact that they have the same ip address assign, ok put it this way every host HAVE to have an ip address assign differently of course even tough they are connecting to a hub? or assigning an ip address to this hosts at this layer (layer 1) does it really affect the way they can communicate?

can they communicate without any ip address or they have to have an address assign no matter what?

I don't know if you understand what I'm trying to expose here

more simple hosts connected to a hub can they communicate base on their mac address or not ?

thank you

alan2308

E1or0 wrote: »

Networker I understand how Hubs and Switches work back to the main question, why 3 out of 7 computers connected to a hub with the same ip address assign, manually assign can give you a conflict when a hub is not even a layer 3 device, its layer 1 and does not use arp.

why 3 computers that connects to the same hub cannot communicate do to the fact that they have the same ip address assign, ok put it this way every host HAVE to have an ip address assign differently of course even tough they are connecting to a hub? or assigning an ip address to this hosts at this layer (layer 1) does it really affect the way they can communicate?

can they communicate without any ip address or they have to have an address assign no matter what?

I don't know if you understand what I'm trying to expose here

more simple hosts connected to a hub can they communicate base on their mac address or not ?

thank you

With conflicting IP addresses, the computers will still be able to communicate at Layers 1 and 2, they just can't communicate at Layer 3. The hub is in no way stopping them from communicating.

networker050184

I don't think you understand how ARP works which is why you are confused. Answer these and I think you might get it.

Q - How does a host get another hosts MAC address?

A - ARP!

Q - How does ARP work?

A - One host sends an ARP request to the IP ADDRESS of the other host to find its MAC.

Could they communicate without an IP address? Yeah if it was designed to work that way, but it isn't.

NONE OF THAT HAS ANYTHING TO DO WITH THE HUB!!!!!

burbankmarc

All applications operate using TCP/IP. They use IP addresses, not mac addresses.

alan2308

burbankmarc wrote: »

All applications operate using TCP/IP. They use IP addresses, not mac addresses.

Only if you're lucky enough to live in an entirely TCP/IP world. Not everyone gets to pretend IPX (or anything else for that matter) doesn't exist.

E1or0

Networker Now I get a clear understanding of everything, I called a collie of mine that had this issue with a client of him he confirmed that there was a router connected to this hub, the device causing the ip conflict was the router it self and not the hub, I always thought he had only a hub and several hosts connected to it, that's why I opened up this thread to clarify my self with this whole idea of the hosts connected to this hub not been able to communicate among them due to this ip conflict message he was receiving when the hub is a layer 1 device that only floods what enters a port to every other as an ( extender or repeater )

Now I understand what happened to him he never mentioned to me the router lol

he corrected issue by removing the ip address manually assigned to the 3 hosts and set them up in dhcp, ip addresses conflict corrected

Thank you again all and sorry for the misunderstanding my friend didn't specified

zerglings

burbankmarc wrote: »

All applications operate using TCP/IP. They use IP addresses, not mac addresses.

Not all applications operate using TCP/IP. I am sure you know that. c",)

E1or0

Zerglings I'm sure burbankmarc knows that, the sad part is the one of giving out wrong information

hex_omega

alan2308 wrote: »

Only if you're lucky enough to live in an entirely TCP/IP world. Not everyone gets to pretend IPX (or anything else for that matter) doesn't exist.

I feel for you. I truly do.

veritas_libertas

dynamik wrote: »

Yea, I was going to say, Paul's computer must suck. I use an L7 computer that has applications.

(We actually just gave him an old Linksys switch with a Fischer-Price front-end. It's been keeping him busy for hours.)

Okay, that was just funny! Best slam I have heard in a while...

chX

This is how I like to look at it (please let me know if I'm wrong about anything, half of the reason I'm writing this is to see how much I really know)

Networks, Ethernet, all of that is created to work in a specific way. In the case of TCP/IP and Ethernet, that's IP addresses and MAC addresses, and you will see the importance of having two addresses rather than one when you look at moving data from your LAN out to a WAN somewhere (or even a different network, really).

The PC will move down the layers and encapsulate data at each layer. It gets to the Network layer, and it knows its own IP address, and it *should* know the destination IP address (You'd specific it in a command like ping, or it would resolve hostname -> IP address).

Then it gets down to Layer 2, and it encapsulates everything into a frame. It knows the source MAC address, but it may not know the destination, so it will ARP for that.

From the PCs perspective, it's irrelevant what is connected on the other end. Really, only a few things could happen:

1. It'll compare the destination IP with its own IP address and Subnet mask and realise the other host *should* be on the same network, so it will just ARP for that.

2. It'll compare them and realise it's on a different network, so it will ARP for its default gateway, and if no gateway is set it will drop the packet.

I think it's important to realise the data itself never changes, regardless of whether it's being sent to a hub or a switch or a router. The difference is the hub really doesn't understand 1s and 0s, it doesn't know what they represent, it just sees varying voltage and cleans up that signal then retransmits it out all of the ports except for the one it came from.

The other PCs will understand, however, and will reply to that ARP. Then the original PC will be able to send a complete frame across (Hub won't really understand it, but it will get there and the PC will accept it.)

E1or0

Very good chx