2 NIC trouble connecting Cable Modem & Printers

Hope someone can help: I had a Windows XP computer setup for someone with dial-up. The NIC was hooked up to an 8 port switch which was hooked up to a Xerox color printer. Then I hooked up a DSL modem. Since there was no open NIC, I connected the modem to the switch, and set the IP, Subnet & Gateway on the printer panel to match the static DSL address given by the provider. This worked fine.

Then here's the problem: Switching from DSL to cable modem. Cable guy came and tried to connect the cable modem (Motorola SBV5120) using USB. (USB becomes another NIC for the computer). Seems this didn't work, because the computer thinks that the switch is the internet gateway! So the guy disconnected the switch (and printer) and left it that way... (Said it was "interfering ".)

When I came, I reconnected the switch, put in a second NIC in the PCI slot, connected the modem to that, but it wouldn't work! So I disabled the original NIC in the device manager and immediately got on the net! So then I re-enabled the original NIC and managed to be able to talk to the printer too. I thought "problem solved!" Well, not quite.

Problem: once I rebooted--no internet connection again!!! The computer picks one or the other and I don't know how to make always use the NIC connected to the cable modem as the internet "gateway ".

(Temporary fix: I connected the cable modem the same way I did the the DSL and I changed the IP on the printer to match the cable modem. Somehow I suspect there is some conflict there too because the printer doesn't always respond to ping so well. Most obvious solution of course is to add a broadband router.)

But I'd like to know more--what's the significance of setting a public IP address on the printer and its NIC/Switch? Is the public IP I selected the problem? What does public vs. private IP have to do, if any, with the computer getting confused between the "internal printer network" and the WAN IP? Does the "Gateway" address I set on the NIC/Printer have anything to do with the problem? Maybe I should not set a gateway on the Printer NIC? (ie. does the computer look for the card that has a gateway set to connect to the "WAN "?)

I remember having 2 nics in my computer and having one hooked up to cable modem and the other hooked to a hub where I connected other computers and could browse the web. The computer never got "confused "... I understand this is a usual setup. The computers inside have private addresses 192.168.x.x. But I don't know if that's where the problem is occurring... Help!!!

Thanks,
Tek.

 

Ok hardware list
Xerox Colour Printer w/NIC
8 Port Switch
1 Computer 2 NICs
Cable Modem
**Please confirm list**

First remove the extra NIC from the computer, its not needed.

Do you know the IP of the cable modem?

If you do then your almost set.

Connect the cable modem to the switch, set the IP of the computer and printer to whatever (with in the same range of each other) (e.g. 192.168.0.2 for computer and 192.168.0.3 for printer) you get the drift. Set the Subnet to 255.255.255.0 then the gateway set it to the IP of the cable modem. The printer doesn't need the gateway unless you want people to print to it over the Internet. Set your Primary DNS to the IP of the cable modem. After doing that you should be up and running.

If all else fails get a cheap router and go from there.. It will take the hassel out of the whole thing.

Private IP 10.x.x.x or 192.168.x.x (for internal LAN and free to use people on the Internet can't see you)
Public IP (What the ISP gives you and how people on the Internet find you)
Gateway (the IP of the device that talks to the internet, usually public IP)

Please post results

 

Thanks Dcrypter! I'll try this next week and let you know what happens. So you say that the computer got confused between the two cards because I entered a "gateway" address on the card I hooked up to the printer, and the gateway address specifies a "gateway" to another network--ie. the internet?

What confused me is that there is a default gateway address entered in the printer. For example, there is another printer there that I want to hook up too, it has a jetdirect print server and the default address is 192.168.10.35 and so is the gateway address. (Subnet mask is 255.255.255.0...) So I thought I need to enter the gateway address too.

 

Hi TekWiz. Let me give you a sort of general network overview that may help clarify things for you. This will be confined to information that applies to your variety of small, private, non-routed, TCP/IP network (and that disclaimer is to keep experts from jumping on me for oversimplifying some things).

First off, I think the Cable Guy who came wasn't particularly technical and got confused. Unfortunate but it certainly does happen.

Next, a suggestion. USB is great and is the best option for lots of things. At this point, networking IS NOT one of them. If you possibly can, I strongly suggest you stay with regular ethernet network cards and avoid USB for any networking. DSL and cable both make perfectly good modems that have an rj-45 ethernet port (like a phone plug but larger). Sometimes USB just doesn't work right with networking and quite often, no one ever figures out just why.

Network - a group of devices using TCP/IP that use a combination of IP address and subnet mask that place them on the same logical subnet / network. Devices on the same logical network (and that's the only meaning for 'network' as I'll be using it) can easily work with each other as long as they are connected together by being plugged into the same switch or hub or cable.

Private network - a network IP address must be unique within the network. Same as with a house address for postal delivery. There can only be one 312 Rose Street, Boulder, Colorado (although you can have as many 312 Rose Street addresses as you have towns). When the internet was first designed, 3 ranges of IP addresses were classed as Private which meant they would never be assigned to any organization. I can use a private address range and you can use the same one. As long as our two networks never need to communicate directly, there is no confusion.
192.168.x.x is private and probably the best to use for most small networks since it also is a small range.
172.16.0.0 - 172.31.255.255
10.x.x.x

Most home office systems with a router/switch will use 192.168.1.x or 192.168.0.x with a subnet mask of 255.255.255.0. If you have your own router, you should go with the range it wants to use.

If you are using a subnet mask of 255.255.255.0 all devices from
192.168.0.1 to 192.168.0.254 can talk with each other
192.168.1.1 to 192.168.1.254 can talk with each other
192.168.1.1 and 192.168.0.1 cannot work together without some serious help.

Pretty much all other IP addresses can be publicly assigned which means they need to be unique. What you get from your ISP is a unique, public IP address. If you have a single PC, it will have that public address assigned. If you have one of the router/switches made for home offices, the router will have the public address assigned and will deal with any devices plugged into it's switch ports.

Gateway - If I want my network devices to talk to the outside world, I have to put in the address of something that knows how to talk to the outside world - normally a router. That way, if I request an address that is outside my local network, the request is sent to the gateway address I have listed and if that is a router, it will forward the request outside my network. If I have no gateway address listed, requests will simply die.

A PC on my local network that needs to get to the internet must have a gateway address. That is normally the private address of my router. A printer on my local network should not ever need to communicate to the outside world and should not have a gateway address in the network card settings.

~~~~~~~~~~~~~~~~~~~~~~~~~~

The above was pretty long and may have been confusing. If so, say what part and we'll take a stab at clarifying that part. Same if it left you with more questions. Just ask.

 

My early Sunday Morning Not quite awake ideas.

Unless I missed it I do not see a very helpful piece of equipment mentioned.

You already have the NICs.

If I read correctly the Printer also uses a NIC. It is plugged into the Switch already I believe.

Now How about adding a Device called a Router ?

Plug the machines and the printer into the Switch. Or if you do not have more than four devices plug them right into the Router. The LESS equipiment inline on a LAN the better.

Plug the switch into the Router.

Connect the Cable Modem and the Router.

Set things to Automactic which causes the Router to be a DHCP server and auto assigns the Addresses. And with the Router/switch combo you can ( or should be able to ) add several machines.

I have three machines and a Printer plugges into a Switch/Router Combo. The Printer does get left on 24/7 becuase any machine may want to use it.

BillyBob

 

And added after thought.

When setting up a home LAN it is best ( if possible ) to use all parts made by the same maker.

ie: All of my equipment is Linksys.

My original Cable Modem was an HP. It seemed to have problems so I replaced it with a Linksys. NO PROBLEMS since.

BillyBob

 

Coming in late and trying to simplify.

Looks like the DSL Modem had routing capability built in and the Cable modem does not.

Purchase a Cable / DSL Router (Linksys, D Link, yada yada)
Plug the cable modem into the WAN port of the router. If you have enough ports eliminate the switch otherwise plug the switch into one of the LAN ports on the router.

Now there may be a hiccup in this process. The Cable ISP may be using MAC address filtering to keep unauthorized accounts out.

You may have to call the cable company and give them the WAN side MAC address of the router because this is what they will see instead of the original PC.

 

Thanks to all of you for all the info!

My comments:

Newt:

I think it was worse than "confused" It is disappointing that a cable company that charges $150 for business installation sends a "professional cable installer" who disconnects the printer in order to get the modem to work, plugs it into the FRONT USB port (Unsightly) when there's a USB hub on top of the computer and then leaves it that way mentioning that the switch/printer is "interfering "... The guy hardly knew English either... When I called tech support they weren't interested, and wrote it off as a "non-standard setup." Looks like their instructions are "Just get 'em online no matter what it takes! Let the customer deal with any problems later--we'll just charge 'em another $100 for a return visit if they call us.

BTW: The same week, someone else had a cable modem installed at home--two guys came, one jumped in the pool with no permission. They provisioned the modem without setting up the email address (part of the provisioning process), and when I came to set up Outlook, I had to help the customer call up Cablevision and get them to supply her with an email address.

Sure it isn't--in fact when I initially got my SB4100 Motorola modem and connected it to USB (too lazy to install the NIC) I had blue screens when downloading. Now, when I tested the throughput using myspeed.visualware.com with the SBV5120 USB, I got about 3500 Kbps and 9700 Kbps with the NIC!!! This is the latest modem and only has USB 1.0. Looks that's a good way to CAP your broadband to 1/3 of the speed! Maybe that's why they include USB--the cable company loves 'em.

Thanks for the great explanation of private addresses and gateways. While I did read some pages about that on the web, your explanation made it clearer and more understandable!

BillyBob: Since originally the computer only had dialup access, the internal network card was only used for the Xerox printer--the switch was there for only one reason--to interface the computer to the printer since a crossover cable didn't work (Ancient printer only has a 10 card, not 10/100--I'm not even sure the crossover cables work with two 10/100's, maybe only on the old fixed 10 or a fixed 100.) So when the DSL modem arrived I simply connected it to the switch instead of putting in another card or adding a router. When I set the address of the printer to the same address as the modem gave the card, it worked.

I didn't know if the cable guy would know to do the same. Obviously he didn't. I did the same and it works now. Although the data doesn't seem to get to the printer quickly--maybe because I put in a wrong gateway address. I'll have to check that this week.

My original instinct was to just put in another network card just for the modem and keep the same setup for the Xerox and another printer (an HP5000 with a Jetdirect card) which I'm trying to connect--keep them SEPARATE just to help keep things more potentially trouble-free.

Yeah, BillyBob--Now I can appreciate the advantage of using the same brand. However it's not always possible. It is very strange that the Motorola modem didn't want to recognize the internal DAVICOM NIC built into the SOYO motherboard. But I think this is pretty rare...

Scott--

Not sure how you gathered that? How is the cable modem different? Are you referring to the slowdown of data to the printer? Otherwise it appears to work the same as the DSL modem--both worked when connected to the switch with the printer.

Yeah, I know a router would be a simple solution. But I didn't think that having the modem hooked up to its own NIC and the printer to another NIC with the switch was a bad idea as a starting point. I was trying to keep expenses down for my friend.

One thing I'm wondering about, why would the cable company want to "marry" the modem to a particular network card??? I mean, there is only one modem registered per account--what do they care what you plug it into? It's sort of like the phone company registering the phones you got plugged in.

But Cablevision doesn't do this--I think they did register the MAC addresses of cards they supplied to some customers and now prevent those cards from being used with other modems for some strange reason, but other than that, the modems will give a new IP address to any device you connect them to if the power is cycled. However maybe an insight into this might be that now Cablevision is keeping addresses static--as long as the device is the same. So if you plug the modem into your laptop it will be one address and will stay that way indefinitely, and then if you plug it into your desktop it will give another address and remain that way. So maybe they marry addresses to devices and that's why the same NIC that was married to a modem won't work with another modem, but if the MAC address is changed in the device manager, it will. (BTW I didn't know the MAC address could be changed on devices so easily--how is it done in Linux, (is there a device manager too? or through some command? anyone know?)

Tek.

 

I myself question using the address of the card. But I also realize the possibility of other ISPs doing different. Other setups may be different.

The 2nd Cable Modem that my ISP installed was a HP. It was not working as it should so I went out and bought and installed a Linksys Cable/DSL Modem. So now my NICs, Swtich, Router and Modem are all Linksys. I did nothing with the cards themselves.

After getting everything hooked up I called my ISP and just gave them the MAC address of the new modem. In less than 2 minutes I was back online. And all while the tech was still on the phone.

So. Unless I am wrong ( or others do it different ) the MAC address of the Modem is used.

In my case the Router takes care of the machine addresses using 192.168.1.100 through 192.168.1.103 in my case. ( only 4 units connected ) And the address of a specific machine ( except the Printer which is unually always on ) varies from 101-103 according to which one it powered up first.

I just looked and Rip ( 3rd machine ) is 101. Nancy ( 2nd machine ) is 102 and I ( Bob ) am 103. So that tells me Rips was the first machine on today. And the address does not change till the machine(s) is(are) POWERED DOWN.

BillyBob

 

Some ISP's do it as an additional security measure.

I deal with this everyday and in my Market both Cable ISP's (Knology and Charter) have a modem that are simply a connection point to their network.

You get a Public IP and only one IP so you need a router to create a private Network with NAT

Knology uses MAC filtering and Charter does not.
You may not be aware of this but MAC address filtering is not rare by anymeans. Look in the configuration pages of any Cable\DSL rotuer and I will bet you a dollar to a doughnut you will find a page called "MAC Address Clone" for that very reason.
Some ISPs do this because they only want one NIC connected to their network and before MAC clones came along you had to Lie to them and say "I got a new computer" to have an excuse to change MAC addresses.

In my market Bellsouth the DSL provider has DSL modems with a manageable NAT. Both Cable companys do not and never have.

 

I did. And there is. Router = Linksys BEFSR41

BillyBob

 

BillyBob and Scott, Yeah, I know that they tried to avoid people hooking up the modem to more than one computer--to get you to pay extra for additional modems. But these days, cablevision, for example, actually gives a free promo netgear wireless router! It became a fact of life that people will be able to do this, so they gave up their greedy ideas.

Obviously the modem MAC *HAS* to be married to their network, otherwise anyone would be able to connect any modem to the network and get online. In fact someone called me and asked me why he wasn't able to get access with the Linksys modem he bought from Staples!!! And this guy was an M.D.! People really tend to underestimate large corporations and that's an understatement. If they were so stupid they would have never gotten large... But that's off the topic..

Also, I seem to remember that modems like the Motorola line are able to supply private IPs? But this function was and is disabled? Or am I dreaming?

I recently became aware of "MAC Cloning" regarding the SunRocket VOiP adapter. It has this in the setup--I guess if you get another unit and want to use it with the same account...

So I am aware of this practice of marrying the modem to the card, but I was surprised to hear that Cablevision which doesn't do this, still keeps a list of MACs for cards they gave out and another modem will not give these a IP, while it will happily give an IP to any other NIC... Strange...

Scott--what do you mean "as a security measure ". Security against what? Someone stealing the modem and using it elsewhere? But there is only one registered modem...

Tek.