Network Help please

[draftermatt]

Office set up is 6 computers. Our cable modem has 4 ports.

To remedy this problem I had a switch/hub plugged into one port on the modem, 3 PC's plugged into the modem and 3 plugged into the hub.

Few weeks ago big electric storm, fried modem and hub.

Comcast gave us a new modem, we obviously had to get a new hub.

For the time being I had the most important 4 PCs plugged direct to the modem.

Went out today and bought a Switch. Tried to plug it directly into the modem, and do 3 PC's again, and promptly got no connection to any PC.

Called Manuf. and was told that I NEED a router now. I need to plug the router into the modem, and the switch to the router, and then the PCs into the switch only.

Is this the only way I can do this? Or is there anyway I can go back to my old set up.

[WinterWolf]

If your ISP gives you 6 IPs, it should work the way you have it. If not you need a router.

This assumes that the hardware you have now is identical to what you had before. Also if your hub has a dedicated WAN port try using that. Or if you are using it, try plugging the cable from the modem into one of the LAN ports.

HTH

[Pedersen]

If you have a cable modem with multiple ports on it, it's almost guaranteed to be a router.

Very likely, what has happened is that your switch and your cable modem are not auto-sensing. Without getting into a whole slew of details, you have two choices, really:

Option 1: Look at the switch. One of the ports will be labelled "uplink", or have a diagram that looks something like an X next to one of the ports. Same will be true on the cable modem. Attach a regular ethernet cable to those ports, and you should be fine.

Option 2: Go to Radio Shack, Best Buy, or some other mildly specialty electronics store. Find a salesperson, and tell them you need a crossover ethernet cable or a crossover adapter for an ethernet cable. Total cost should be less than $10. Using that, you should be able to plug any port on the switch into any port on the cable modem (aside from the aforementioned uplink ports).

Either of those options should work just fine.

[Eric the Grey]

It almost sounds to me as though you should have just purchased another Hub, instead of a Switch. A hub is just a dumb pass-through device. When I say dumb, it knows just enough to pass the data back and forth to the right devices, but not much more. The switch is trying to do more, and probably messing things up in the process.

Now, I'm not great at networking, but this seems the easiest fix.



Eric the Grey

[Der Cute]

Your goal is to have:

CableModemRouterThing (doing DHCP/NAT) ---------3 pc's and 1 link to switch---------Switch---all the other PC's.


Thought: Is the CableModemRouterThingy a router or what. List make/model etc.
Whos' the carrier?
Some Cable Modems are just modems, and some are actually routers.
And Some carriers only release 3 or 4 IP addresses.

Pedersen is correct; find the Uplink port on the Switch. Connect that to the Cable Modem Port 1.

Connect a PC to CM, and one to Switch. Check each pc if they get a 192.168 address. (start, run, cmd, ipconfig/all)
Make sure the ones on the switch can ping out to somewhere else in the world....
start, run, cmd, ping www.yahoo.com

I"m wondering if the firmware in the cable modem is restricting address leases.
Can you get into the cable modem? should be something like 192.168.0.1 and admin admin for username/pw. We'd need to see what it's set up to do, DHCP or pass through.

Cutenoob.

Sorry if it's too technical.
Post some pics

[Pedersen]

It almost sounds to me as though you should have just purchased another Hub, instead of a Switch. A hub is just a dumb pass-through device. When I say dumb, it knows just enough to pass the data back and forth to the right devices, but not much more. The switch is trying to do more, and probably messing things up in the process.

Actually, that is not quite correct. For the home user, there are four separate device types. They can be mixed/matched, but they break down to four types. In fact, this breakdown holds until you get into very large scale networking. Even then, it's true, it's just that there are specializations within them at the scale of (for instance) Akamai, Rackspace, etc.

Those types are as follows:

• Hub: Very dumb device. Receives packet on port X, and sends that packet on to all other ports on the hub. Does not care about contents in any way, shape, or form.
• Switch: Smarter device. Uses the layer underneath IP addressing. At this layer, each device has a local MAC address. The switch examines the packet coming in on port X, and looks for the destination MAC address from that packet. It then forwards the packet on to that port and that port alone. No other port is affected.
  
  This is the critical difference between hubs and switches. a 100MBit hub will provide the same 100MBits to all connected devices. A 100MBit switch can provide 100MBits to any given device pair. So, an 8 port 100MBit switch can have 4 100MBit conversations happening at the same time without any slowdown amongst them. An 8 port 100Mbit hub can only provide 25MBits to each of those same 4 conversations.
• Firewall: This device is responsible for examining packets on their way in and out of the local network. It can permit or deny the traffic based on a number of rules. For instance, it can allow http/https inbound, and deny all other inbound traffic. It can also be configured to say "The computer with the local ip address 192.168.1.101 is not allowed to communicate with the internet server at ip address 94.136.36.64 between the hours of 9pm and 8am" (for example). The rules can be quite complex, depending on the firewall that implements them.
  
  As a rule, the firewall is the device that is actually responsible for Network Address Translation, which is what lets you have multiple computers share the same internet connection through your ISP.
• Router: This is the device that is actually responsible for getting data out to the internet, and from the internet back to your network. Technically, it's what manages the connection between your network and any other network, but usually is used for the internet/local network management. It receives the data from the firewall, and forwards it out. At the same time, it receives from the internet, and sends to the firewall.

I've glossed over a lot of the details here, but those are the devices. Your typical home router actually has the router, firewall, and a switch built into it. From the user's perspective, it's all one device.

Oh, and from what I understand of wireless, any given wireless access point is more like a hub than a switch.

Hope that helps clear it up a bit.

[draftermatt]

Thanks for the ideas.

I tried to get a hub but the switch was all Radio Shack had. So it's my fault I bought it assuming it would work the same.

All I need is the hub (dumb device), so I'll start there. If I'm still having problems I'll try other routes suggested.

It's a Comcast provided modem. SMC Networks.

The odd thing about the switch was it had no input port. Just 5 Cat5 ports and a power port, which seemed odd when I pulled it out of the box.