Router Or Switch

I have never fully understood the difference between routers and switches
(even though my home network has both) and cannot, for that reason, answer a
friend's question. Maybe someone here would help.

The question is that he has a cable connection from NTL (as was) that uses a
cable modem connected to his PC via Ethernet. He now wants to add an
additional PC and wants to know whether he needs to connect a router between
the modem and the two computers or would a switch do the job.

Thanks for reading this.
--
Keith Willcocks
(If you can't laugh at life, it ain't worth living!)

"Keith Willcocks" <(E-Mail Removed)> wrote in message
news:0ZCdnWB-(E-Mail Removed)...
>I have never fully understood the difference between routers and switches
>(even though my home network has both) and cannot, for that reason, answer
>a friend's question. Maybe someone here would help.
>
> The question is that he has a cable connection from NTL (as was) that uses
> a cable modem connected to his PC via Ethernet. He now wants to add an
> additional PC and wants to know whether he needs to connect a router
> between the modem and the two computers or would a switch do the job.

A router connects one network to another. It operates at layer 3 of the OSI
model, see:
http://whatis.techtarget.com/definit...523729,00.html

A switch carries data packets from one computer to another, irrespective of
protocol. It operates at layer 2.

In your friend's case the modem brings the ISP's network to his house; but
the ISP's network is almost certainly configured to communicate with only
one computer.

He therefore needs a router. One side (the public or WAN side) of the
router connects to the cable modem. The other side (private, or LAN)
connects to his computers. As a matter of convenience the router will
normally contain a switch on the LAN side.

--
Graham J

On 16 Mar 2007, "Keith Willcocks" wrote:

>The question is that he has a cable connection from NTL (as was) that uses a
>cable modem connected to his PC via Ethernet. He now wants to add an
>additional PC and wants to know whether he needs to connect a router between
>the modem and the two computers or would a switch do the job.

A router is used to connect two different networks and 'route' packets (that
meet certain criteria) between them. He needs a router to provide a way to
share the single IP address from the WAN (cable) to more than one LAN IP.

Traffic from LAN IP #1 to #2 (eg copying a file) is not passed by the router
out onto the internet, but requests to access a web / mail / news server on
an IP which isn't part of the LAN will be routed out to cable and the data
that comes back is routed (assuming NAT is in use) to the correct LAN IP.


As for getting a router onto the cable service, see earlier posts (so the
cable service accepts the router in place of the single PC currently using
the connection). In the past it was sometimes a little awkward because the
cable side was looking for the same MAC address (hardware identity for the
ethernet interface, look in Wikipedia for more on this type of MAC). HTH

In article <0ZCdnWB-(E-Mail Removed)>, Keith Willcocks
<(E-Mail Removed)> writes
>I have never fully understood the difference between routers and switches
>(even though my home network has both) and cannot, for that reason, answer a
>friend's question. Maybe someone here would help.
>
You require a router to connect between networks e.g. your home network
and the Internet or between 192.168.1.0/24 and 192.168.2.0/24.

A switch will allow you to connect different devices on the same
network.

Thing do get a bit more complex e.g. boxes like the Vigor 2900 have a
router and switch inside.

Switches are also getting more complex (to keep the price up) and can do
routing as well but probably in business price ranges.


>The question is that he has a cable connection from NTL (as was) that uses a
>cable modem connected to his PC via Ethernet. He now wants to add an
>additional PC and wants to know whether he needs to connect a router between
>the modem and the two computers or would a switch do the job.
>
>Thanks for reading this.

I use a Vigor 2900 for the above task.

--
Bob Geddes

"Keith Willcocks" <(E-Mail Removed)> wrote in message
news:0ZCdnWB-(E-Mail Removed)...
> I have never fully understood the difference between routers and switches
> (even though my home network has both) and cannot, for that reason, answer
a
> friend's question. Maybe someone here would help.
>
> The question is that he has a cable connection from NTL (as was) that uses
a
> cable modem connected to his PC via Ethernet. He now wants to add an
> additional PC and wants to know whether he needs to connect a router
between
> the modem and the two computers or would a switch do the job.

Your friend needs a router, as others have said, but it needs to be a
Cable/DSL router, and there should be NO mention of ADSL Modem on the box
;-)

P.

"Keith Willcocks" <(E-Mail Removed)> wrote in message
news:0ZCdnWB-(E-Mail Removed)...
>I have never fully understood the difference between routers and switches
>(even though my home network has both) and cannot, for that reason, answer
>a friend's question. Maybe someone here would help.
>
> The question is that he has a cable connection from NTL (as was) that uses
> a cable modem connected to his PC via Ethernet. He now wants to add an
> additional PC and wants to know whether he needs to connect a router
> between the modem and the two computers or would a switch do the job.
>


Thankyou for the prompt responses. I have now advised him to look at a
cable/DSL modem-router.

Thanks again.

--
Keith Willcocks
(If you can't laugh at life, it ain't worth living!)

On Fri, 16 Mar 2007 17:21:31 -0000, "Keith Willcocks"
<(E-Mail Removed)> wrote:

>
>"Keith Willcocks" <(E-Mail Removed)> wrote in message
>news:0ZCdnWB-(E-Mail Removed)...
>>I have never fully understood the difference between routers and switches
>>(even though my home network has both) and cannot, for that reason, answer
>>a friend's question. Maybe someone here would help.
>>
>> The question is that he has a cable connection from NTL (as was) that uses
>> a cable modem connected to his PC via Ethernet. He now wants to add an
>> additional PC and wants to know whether he needs to connect a router
>> between the modem and the two computers or would a switch do the job.
>>
>
>
>Thankyou for the prompt responses. I have now advised him to look at a
>cable/DSL modem-router.
>

No - this is wrong. It must *not* be a 'modem-router'. That
normaly implies an ADSL modem router. What you want is a cable router
- note that the word 'modem' isn't in that name!

Just to confuse things, many cable routers mention DSL on the box,
but the important thing is that they *don't* mention a modem!

Regards,
Harry.

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"Keith Willcocks" <(E-Mail Removed)> wrote in message
news:(E-Mail Removed)...
>
> "Keith Willcocks" <(E-Mail Removed)> wrote in message
> news:0ZCdnWB-(E-Mail Removed)...
>>I have never fully understood the difference between routers and switches
>>(even though my home network has both) and cannot, for that reason, answer
>>a friend's question. Maybe someone here would help.
>>
>> The question is that he has a cable connection from NTL (as was) that
>> uses a cable modem connected to his PC via Ethernet. He now wants to
>> add an additional PC and wants to know whether he needs to connect a
>> router between the modem and the two computers or would a switch do the
>> job.
>>
>
>
> Thankyou for the prompt responses. I have now advised him to look at a
> cable/DSL modem-router.
>

there is NO modem in a Cable/DSL router,none at all, none whatsoever,
capiche?
He doesn't want a router with a modem, he already HAS a modem ;-)

P.

On Fri, 16 Mar 2007 12:25:33 GMT, in uk.telecom.broadband , Bob Geddes
<(E-Mail Removed)> wrote:

>Thing do get a bit more complex e.g. boxes like the Vigor 2900 have a
>router and switch inside.

Most retail routers have a switch inside - the switch is what gives
you the 4 LAN ethernet ports. The router routes between the LAN and
the WAN ports.
--
Mark McIntyre

Bob Geddes wrote:

> Switches are also getting more complex (to keep the price up) and can do
> routing as well but probably in business price ranges.

There are some switches coming out of China that do VLANs/routing for under
a ton. Expect to see them on eBay soonish. Although that's about 10x what a
home user wants to pay ;-)

--
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