Cable routing question from ADSL user

[Jimbo]

Hello
I curently have an ADSL router fitted to my telephone line. It has 4 ethernet ports which feed 3 PCs very nicely.
I have cable TV ( Telewest as was ) and I am considering Virgin cable broadband. Not sure of the setup.
Would I need a new "cable" router ?
Would this replace some Virgin kit or connect to it ?
Could I put the ethernet feed from Virgin into the spare port on my ADSL router and use it just as a router ie no ADSL connection?
Thanks
Jim

[danielf]

Unless you have a router that is suitable for both ADSL and Cable you will need a new one, as standard ADSL routers do not work on Cable (nor do standard Cable routers work on ADSL). The linksys WRT54G is a popular choice around here. Virgin will provide you with a modem which you plug into the router. From there, your setup will be the same as it is now.

[Jimbo]

My ADSL router has 4 ethernet ports.
Given that the feed from Virgin is ethernet I would have thought that the router would still route traffic across the 4 ports. Granted the ADSL port would not be connected.
Jim

[danielf]

Originally Posted by Jimbo

My ADSL router has 4 ethernet ports.
Given that the feed from Virgin is ethernet I would have thought that the router would still route traffic across the 4 ports. Granted the ADSL port would not be connected.
Jim

The 4 ethernet ports on your router are output ports, not input ports. You need a router that will accept the ethernet feed as input. This is then distributed across the (normally 4) output ports. The ADSL port on your current router is an input port, but it is the wrong type.

What make and model is your router?

[Jimbo]

It's a Safecom SAMR-4144.
And from what I know ethernet ports in general are not input or output they are both.
The 3 PCs can all talk to each other through the router.

[Jon T]

Sorry Jimbo, your going to need a new router.

The four ports on your existing router are on one side of the NAT(network address translation) process, and the ADSL feed from your phoneline is on the other. This is what danielf meant when he said that they were only output ports, yes ethernet ports are bidirectional, but in the case of a router only one port(and that can be an ethernet or ADSL port) can take the main IP feed and feed it into the NAT process in your router.

An ADSL router internally is lad out like this:

ADSL Modem <-> NAT/Firewall <-> Ethernet Switch(usually four port)

A cable router is laid out as like this:

Ethernet WAN Port <-> NAT/Firewall <-> Ethernet Switch((usually four port)

So the reason that your PC's can communicate with each other is that they have a direct path to each other via the switch part of the router.

[Jimbo]

OK thanks to all.
I have downloaded the linksys WRT54G manual and the backplane has 5 ethernet ports, quote

Internet
The Internet port is where you connect your cable or
DSL modem through an Ethernet network cable.
Your modem connection will not work from any
other port.

Ports 1-4
These four LAN (Local Area Network) ports con-nect
to network devices, such as PCs, print servers,
and network attached storage (NAS). Each of the
ports will auto-detect whether a straight-through or
crossover cable is plugged into it, so there is no need
for an uplink port. Any one of the four ports can
serve as an uplink port to other network devices.

Jimbo

[Jon T]

Originally Posted by Jimbo

OK thanks to all.
I have downloaded the linksys WRT54G manual and the backplane has 5 ethernet ports, quote

Internet
The Internet port is where you connect your cable or
DSL modem through an Ethernet network cable.
Your modem connection will not work from any
other port.

Ports 1-4
These four LAN (Local Area Network) ports con-nect
to network devices, such as PCs, print servers,
and network attached storage (NAS). Each of the
ports will auto-detect whether a straight-through or
crossover cable is plugged into it, so there is no need
for an uplink port. Any one of the four ports can
serve as an uplink port to other network devices.

Jimbo

Yep, that one will work for you fine.