Home networking for a Dummy

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Agent47

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Hey

So I know a bit about computers and can figure most things out with some research and trial and error. My current specific issue has been bugging me for a couple of months now and was only introduced to MyBB about a week ago.

I have an ADSL router (as I was lucky enough to have ADSL at my previous house) that cannot take a 3G sim. I hope someone can give me some advice as to if and how I can connect to 3G via my MTN 3G modem and then create a wifi network in my house through my ADSL wifi router? I also have a normal Wifi dongle if I can do it via that.

I use Windows 7.

Thank you
 
1. Plug in 3g modem
2. Go to network and sharing centre
3. Right click on the connection (of your 3g modem)
4. Go to Properties and select "allow other computers to connect to the internet through" bla bla bla
5. (and this assumes your router has wifi) log into your router
6. Turn of DHCP
7. Save and restart router
8. Wireless devices should now see an MsHome netwrok
 
It sounds like the problem is that you don't have a USB port on your ADSL router, and thus cannot connect the 3g modem directly to it. It is still possible to make the 3G connection available to the rest of the network, even if it is via your PC.

Without more details on the specific equipment you have available (makes, models, etc), this would be my approach:

* get the 3G modem working on a desktop machine (or laptop that doesn't leave the premises too much). Basically, something with a USB port that can do Internet Connection Sharing (or whatever equivalent exists for your OS). The cheap 3G router mentioned by InvisibleJim would also work for this.

* Since the machine with the modem will be the gateway, and not the ADSL router, you will need to make sure that your clients (other machines on the network) get the right gateway information. Typically, as part of enabling Internet Connection Sharing, that host will run a DHCP server, and hand out IP addresses to the clients, as well as the correct gateway. However, your ADSL router will ALSO have a DHCP server running, advertising itself as the gateway. You can't have 2 DHCP servers running on the same network, so you need to disable the DHCP server on the ADSL router.

* The ADSL router can still function as an Access Point, as well as a Ethernet switch, though, so long as the wireless and ethernet connections are bridged together. In that configuration, DHCP requests will be relayed from wifi to ethernet or vice versa, allowing the machine running Internet Connection Sharing, and the DHCP server to see them and respond.
 
I have a USB on my router but it does not pick up the 3G modem when I plug it in (Netgear DGN2200) and based on some research of the router it seems that the USB is only for the readyshare function.

At the moment I am having trouble logging into my Router as neither the IP nor routerlogin.net takes me to the router even after I have reset it, read on some Netgear forum that it might be due to my pc having the same IP as the router (192.168.0.1) so I will investigate that. So I was able to perform procedures 1 to 4 from YingYang (thank you very much for that).

Thank you RoganDawes this helps me understand the issue a whole lot better, hopefully I will be able to figure this out over the weekend.
 
You would certainly have trouble if you had the same ip address as the router. Either let the router give you a DHCP address, or assign a different one to your PC. e.g. .2

I suspect that part of your problem is the Internet Connection Sharing being enabled, because with your machine acting as the gateway, it is using the same 192.168.0 network by default. Turn it off, and you should be able to get the IP address from the router, then log in to the router, assign it a different address (e.g. .3), then turn off the DHCP server on the router. Finally, reenable the ICS on your PC.

YingYang's steps should have been in somewhat different order: 5,6,7,1,2,3,4,8 in my opinion. :-)
 
Agent47 said:
I have a USB on my router but it does not pick up the 3G modem when I plug it in (Netgear DGN2200) and based on some research of the router it seems that the USB is only for the readyshare function.

At the moment I am having trouble logging into my Router as neither the IP nor routerlogin.net takes me to the router even after I have reset it, read on some Netgear forum that it might be due to my pc having the same IP as the router (192.168.0.1) so I will investigate that. So I was able to perform procedures 1 to 4 from YingYang (thank you very much for that).

Thank you RoganDawes this helps me understand the issue a whole lot better, hopefully I will be able to figure this out over the weekend.
Click to expand...
Hang on there speedy!!! I forgot about something.

Undo everything and FIRST AND FOREMOST turn off DHCP in your router. This is the reason why you can't access it. Sorry about that.

You cannot access the router because the PC's DHCP server already gave it a random IP (once you click the "share this device..." checkbox) and there's no way of knowing what that IP is, well apart from guessing :)

edit:should have refreshed the page, thanks Rogan!
 
Last edited:
RoganDawes said:
You would certainly have trouble if you had the same ip address as the router. Either let the router give you a DHCP address, or assign a different one to your PC. e.g. .2

YingYang's steps should have been in somewhat different order: 5,6,7,1,2,3,4,8 in my opinion. :-)
Click to expand...
Thanks, I realise now :D
 
Awesome thanx so much everyone works like a charm...just wish 3G in this place came close to fixed line 4mb.

This works and I feel like I am back online.

:) :) :) :)
 
YingYang said:
You cannot access the router because the PC's DHCP server already gave it a random IP (once you click the "share this device..." checkbox) and there's no way of knowing what that IP is, well apart from guessing :)
Click to expand...

Actually, to be pedantic, the reason that you cannot access the router is that your PC and the router either both have the same IP address (most likely), or are in different subnets. Routers in general will not just accept a DHCP address from an arbitrary DHCP server on the network, since in most cases, they ARE the DHCP server! As a result, routers are generally configured with a static IP address, in most cases .1 on the network, and again, in most cases, the network would be something like 192.168.0.0.

This was the same address that Internet Connection Sharing allocates to your PC when you turn ICS on, and then it hands out other addresses in the same network to any DHCP clients that ask for an address.

The net effect though, is that you have two machines with the same IP address, and they will obviously not be able to talk to each other at an IP level. (They can talk at the MAC address level, but that is not the same thing at all).

When your machine wants to talk to a particular IP address in the same network, it uses the ARP protocol to obtain the MAC address of the ethernet adapter of the target host. However, since the IP address in question has ALSO been allocated to one of the network interfaces on your own machine, your computer would never send an ARP packet, because it already knows its own MAC address, and knows how to reach itself. Consequently, any attempts to reach the HTTP server on the router would result in a connection being made to a (possibly non-existent) HTTP server on the user's own PC, and most likely failing.

The alternative case, where the PC's ICS decided to use a completely different subnet (e.g. 192.168.1.0), would result in the PC being unable to find a gateway that knows how to route between 192.168.1.0 and the 192.168.0.0 networks, and again being unable to reach the router. This can be corrected by adding an extra IP address on the ICS host (i.e. 192.168.0.2), that is then in the same subnet as the router, and hence able to reach it directly.
 
Hi all,
Great general use input for all here and well described Rogan.
I can confirm that the DGN2200 has a usb but it is for file sharing and not for a 3G card.

Glad that you are back on-line

Regards

Tim
 
Tim the Techxpert said:
Hi all,
Great general use input for all here and well described Rogan.
I can confirm that the DGN2200 has a usb but it is for file sharing and not for a 3G card.

Glad that you are back on-line

Regards

Tim
Click to expand...

Thanks Tim. The other thing I checked was whether there was alternate firmware like OpenWRT for the DGN2200, but it looks like it is running something other than Linux by default, and hence there are no Linux drivers available for the OpenWRT project to use to support the device.
 
Agent47 said:
Awesome thanx so much everyone works like a charm...just wish 3G in this place came close to fixed line 4mb.

This works and I feel like I am back online.

:) :) :) :)
Click to expand...
Glad you're happy, mate! :)

RoganDawes said:
Actually, to be pedantic, the reason that you cannot access the router is that your PC and the router either both have the same IP address (most likely), or are in different subnets. Routers in general will not just accept a DHCP address from an arbitrary DHCP server on the network, since in most cases, they ARE the DHCP server! As a result, routers are generally configured with a static IP address, in most cases .1 on the network, and again, in most cases, the network would be something like 192.168.0.0.

This was the same address that Internet Connection Sharing allocates to your PC when you turn ICS on, and then it hands out other addresses in the same network to any DHCP clients that ask for an address.

The net effect though, is that you have two machines with the same IP address, and they will obviously not be able to talk to each other at an IP level. (They can talk at the MAC address level, but that is not the same thing at all).

When your machine wants to talk to a particular IP address in the same network, it uses the ARP protocol to obtain the MAC address of the ethernet adapter of the target host. However, since the IP address in question has ALSO been allocated to one of the network interfaces on your own machine, your computer would never send an ARP packet, because it already knows its own MAC address, and knows how to reach itself. Consequently, any attempts to reach the HTTP server on the router would result in a connection being made to a (possibly non-existent) HTTP server on the user's own PC, and most likely failing.

The alternative case, where the PC's ICS decided to use a completely different subnet (e.g. 192.168.1.0), would result in the PC being unable to find a gateway that knows how to route between 192.168.1.0 and the 192.168.0.0 networks, and again being unable to reach the router. This can be corrected by adding an extra IP address on the ICS host (i.e. 192.168.0.2), that is then in the same subnet as the router, and hence able to reach it directly.
Click to expand...
You seem like you know netwroking :)

However, ICS will by default always give an IP of 192.168.137.x, and since no router manufacturer implements DHCP around that range his router would always have been on a different subnet. Based on the aforementioned fact your router will never have the same IP as your ICS issuing PC.

Next routers wil accept IP's from any DHCP server if their own DHCP is turned off <- that's how the protol is implemented.

And to point out probably the most important flaw in your argument, if the PC and router are on different subnets ARP does not come into play. ARP is only used within one network.
 
YingYang said:
You seem like you know netwroking :)
Click to expand...

I've been around, but I'm not a huge fan of Windows, so am not intimately familiar with the details of its implementation :-)

YingYang said:
However, ICS will by default always give an IP of 192.168.137.x, and since no router manufacturer implements DHCP around that range his router would always have been on a different subnet. Based on the aforementioned fact your router will never have the same IP as your ICS issuing PC.
Click to expand...

Fair enough.

YingYang said:
Next routers wil accept IP's from any DHCP server if their own DHCP is turned off <- that's how the protol is implemented.
Click to expand...

Nope. It will only do this if the router is explicitly configured to obtain its address via DHCP, as well as having its own DHCP server turned off. I honestly have never seen a consumer router that allows its LAN address to be configured via DHCP, as their 99.99% use case is with a static address, acting as the DHCP server. The remaining 0.01% is with the DHCP server turned off :-)

YingYang said:
And to point out probably the most important flaw in your argument, if the PC and router are on different subnets ARP does not come into play. ARP is only used within one network.
Click to expand...

Well, yes, but it is still used to find the gateway/router that allows packets to get from one network to the other. The IP packet is put on the wire with the IP address of the target router, but the MAC address of the gateway. It is then up to the gateway to know how to route the packet to get to its destination. Of course, in an ICS configuration, the PC itself thinks it is the only gateway in existence, and knows it doesn't know how to get to the other network, and hence fails to connect to the router. Adding an alias address on the router's network tells the PC how to get there.
 
RoganDawes said:
I've been around, but I'm not a huge fan of Windows, so am not intimately familiar with the details of its implementation :-)



Fair enough.



Nope. It will only do this if the router is explicitly configured to obtain its address via DHCP, as well as having its own DHCP server turned off. I honestly have never seen a consumer router that allows its LAN address to be configured via DHCP, as their 99.99% use case is with a static address, acting as the DHCP server. The remaining 0.01% is with the DHCP server turned off :-)



Well, yes, but it is still used to find the gateway/router that allows packets to get from one network to the other. The IP packet is put on the wire with the IP address of the target router, but the MAC address of the gateway. It is then up to the gateway to know how to route the packet to get to its destination. Of course, in an ICS configuration, the PC itself thinks it is the only gateway in existence, and knows it doesn't know how to get to the other network, and hence fails to connect to the router. Adding an alias address on the router's network tells the PC how to get there.
Click to expand...
Hope you don't think I'm looking for an argument here :D
 
RoganDawes said:
The other thing I checked was whether there was alternate firmware like OpenWRT for the DGN2200, but it looks like it is running something other than Linux by default, and hence there are no Linux drivers available for the OpenWRT project to use to support the device.
Click to expand...

A little more searching turned up this site, which may be of interest. It sounds like you *might* find other people who may be interested in adding 3G drivers to the router's build, along with their other extensions.
 
It Depends !

RoganDawes said:
Nah, just making sure that anyone else reading gets the right info :-p
Click to expand...
Some [routers] can do more than others :)

Proxy ARP

The Definitive Guide


BootP and DHCP

BootP vs DHCP

DHCP Relay


Routers CAN forward a lot of stuff -- IF so configured.

ip forward-protocol

ip helper-address


Do Cisco routers block or forward broadcasts?
Ask a CCNA and he will say Cisco routers block broadcasts.
Ask a CCNP and he will say that yes indeed, Cisco routers forward broadcasts.
Ask a CCIE and he will respond wisely "It depends".
Click to expand...

How to Enable Browsing Using NetBIOS Over IP
 
b@nD said:
Some [routers] can do more than others :)

Proxy ARP

The Definitive Guide

BootP and DHCP

BootP vs DHCP

DHCP Relay


Routers CAN forward a lot of stuff -- IF so configured.

ip forward-protocol

ip helper-address



How to Enable Browsing Using NetBIOS Over IP
Click to expand...

OK, funny man! :-) Point made.

I thought it was clear from the context of the thread that I was talking about retail/consumer-level routers.

Of course, Cisco and other enterprise routers can do just about anything you care to name. And, of course, even consumer-level routers can do the same, if you install a more featureful firmware such as OpenWRT on it. But none of that seemed relevant given the context of the original poster's question.
 
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