Why doesn't a hub work for WAN sharing?

You can use a hub.

It all depends on your service provider.

In many places it used to be you were only allowed one IP address and that IP address was locked to the MAC address of one computer. You were supposed to buy an additional line of service for every computer that was to access the internet (or pay extra for additional IP addresses).

A NAT router got around those limitations.

So, to answer your question, a hub will work just fine, but as to how many computers you can connect will be limited by your ISP.

(However, times have changed and now a router is highly recommended as first line of defense (firewall), among other reasons.)

Because your ISP only provides one IP address, and you need some way to share that one IP amongst several PCs. The best way to do that is with a NAT router...

So your IP address is tied to a specific MAC address? Is it the MAC address of the modem or the MAC address of the NIC card attached to the modem via the hub? If the modem broadcasts to everyone connected to the hub shouldn't it work?

Thanks, Derek Basch

The modem may be tied to the MAC address of the ethernet card in the host computer, it may not be (however, I think this is pretty rare now as it causes more service calls and is easily defeated with a NAT router).

You may only have one IP address, you may have more. If you only have one, then only the first device that connects will be able to access the internet, etc.

Normally, your IP address is not tied to a specific MAC address (this is often a premium feature offered by ISPs called static IP). However, it is desired that once a device obtains an IP address it should continue to use that same address if possible. Most DHCP servers will try to do this.

The hub may broadcast (repeat) to everyone, but everyone is going to ignore traffic that is not addressed to them. Google the ARP protocol if you want an intro to how this works. Ethernet does not work well if two devices have the same MAC on the same segment.

Basically, you want to know if a hub will work instead of a router, and the answer is yes, unless certain criteria is met that is controlled by your ISP. You'll have to try and see (or call your ISP). We've already given you the reasons why it might not work or may not work as you hoped.

(But, given that you can often buy a fully featured NAT router for $10 new (after rebates), the question would be why bother with a hub?)

A Hub adds new PHYSICAL (Ethernet) addresses. You will need those in order to attach additional equipment via Ethernet, but that's not enough to share an Internet address. In order to share a single IP (Internet) address, you need something like a NAT router to assert the additional intelligence that's necessary to look inside the Ethernet frames and find, interpret, and manage IP packets inside. Accordingly, most modern, popular NAT routers include a hub or switch so that you will get the required expansion at both levels.

I've published a much better explanation here:

I hope this helps,

-Bob Bosen-

(Instructional Videos for people with work to do)

Becasue it is not "Cable TV"; its "Internet".

For CABLE TV, everyone connected to the medium through a cable, is getting the same data (and enjoying it ;-) ) Its a broadcast. You want to add another node, you just attach yourself to the medium and start receiving, or probably add a repeater/booster if you are far.

Once you start talking about Internet, you are requesting information from servers and getting that specific data. Every different person is sending different requests and thus getting appropriate data. In other words, every connected user has a different session, unlike CABLE TV, where everybody is getting the same information. (Thats another thing, you are watching a particular channel ;-) )

So, in order to make sessions, addressing is needed. This will be a "LIVE" IP address that your ISP will give you. (You can use any IP address for your internal network, but IPs on Internet are all unique). If u have more than one IP addresses given to you by your ISP, you can use a hub for those IPs. If u have only one LIVE IP, neither there is a need for a hub nor adding it will it help extending the network by adding more nodes than the number of supplied LIVE IPs.

Now, further, by using those LIVE IPs, (one or more), you may make your own private networks. Thats your choice. And for that you need a ROUTER or a PC for Internet Sharing.

Regards, ~ Jagmeet ~

And when broadband Internet first came out, especially cable, folks would just plug the modem into their hub (switches were rare in home in the late 90s) and go. Then folks started noticing that they could see the public folder of some neighbors and other printers and what not. Then the cable companies scrambled to change their infrastructure as they apparently didn't think anyone would connect anything other than a single computer or a router. :)

"A Hub adds new PHYSICAL (Ethernet) addresses".

Actually, that's an error. A SWITCH adds a new PHYSICAL (Ethernet address). A hub is actually too dumb to do even that. Three more pubs that you might find helpful along these lines:

(Hubs) (Switches) (Layers)

Sorry to confuse the issue. I hope this helps.

-Bob Bosen-

(Instructional videos for people with work to do)

A modem is not a router.

Every destination on a TCP/IP network must have a unique IP address or data doesn't go where it is supposed to go. The Internet is a TCP/IP network so each connected machine must have a unique address.

Your ISP generally configures his system to provide one dynamically assigned address per customer--you usually have to pay extra for more or for static addresses. In order to access the internet from more than one machine through that connection you have to share that one address among the different machines. There is a technology for doing that, called "Network Address Translation" or "NAT" that is commonly implemented in routers.

A hub does not function at the TCP/IP level, it operates at a much, much lower layer in the OSI reference model and has no capability to provide services of this kind. A switch operates at a higher layer than a hub but still not high enough to provide address translation services for TCP/IP. So you have to use a router.

Wow! Thanks for the replies everyone. Crystal clear now!

I'm not sure that even a swtich adds new PHSYCIAL (Ethernet addresses). The switch _may_ have a MAC address of its own, but is it required to? Perhaps it is better to say that hubs and switches provide more connection points to the Ethernet network?

rick jones

What is this "WAN modem" you speak of?

Presuming your WAN link is a T1 or some other non-Ethernet technology, you obviously need something to convert from one medium to another. In many cases, like cable (aka DOCSIS) and DSL, this is often a simple bridge, in which case you can plug the "modem" directly into a hub. However, T1s and above are rarely bridged to Ethernet because that requires additional, non-standard configuration on the other end, so a router is used. Some cable/DSL providers ship "modems" which are a bridge, router, and NAT/FW device all in one.

S

Rick, I think you're right. The MAC addresses present in managed switches are not required for switch operation. Thanks. It's a fine point (and probably nobody really cares at this point), but what I SHOULD have said would have been more like this:

An Ethernet HUB adds more Ethernet CONNECTORS, but it doesn't understand anything about Ethernet addresses or IP addresses.

An Ethernet SWITCH adds more Ethernet Connectors. It understands Ethernet Addresses, but it still doesn't understand anything about IP addresses. Anyway, the articles I reference before go into greater detail and tell the story better.

Thanks for the clarification!

-Bob Bosen-

(Instructional Videos for people with work to do)

An Ethernet switch very well understand something about IP addresses. Most "layer 2" ethernet switches tend to support IGMP these days, and to do that they need to understand something about IP multicast addresses.

Not to mention layer 3 switches, which by definition always understand IP addresses.

You may want to update your AskMisterWizard.com page on hubs then as it still reads: "However, don't attribute too much intelligence to this hub. It's a pretty dumb device. It only understands Ethernet and Ethernet addresses."

Kind regards,

Ben

Ben:

Thanks. I'll change that page to say something like:

"However, don't attribute too much intelligence to this hub. It's a pretty dumb device. It mindlessly adds more Ethernet connectors, without interpreting any of the transmitted information."

I hope that ends this thread....

Regards,

-Bob Bosen-

(Instructional videos for people with work to do)

Unless it is a managed hub... and such devices do indeed exist (however they are very rare these days)