Home network problems

[Krusty]

Naw, I think I get what you're saying. I was thinking I'd have to use the switch anyways, if there's an upstairs/downstairs setup (which there will be). As it is now we have 4 cables running through a hole drilled in the floor. Having just 1 cable (from switch upstairs to router downstairs) would make things a lot eassier.

EDIT: That's an obvious idea you had there, but I totally didn't see it! Getting a 4-port is literally half the price of an 8-port.

However, I've been asked to inquire whether a router shares IPs or if it gives each connection its own IPs? We have cable modem, which gives you 1 IP, but each additional (and they count, trust me) costs an extra $5 a month, and if we have 1 default and 4 extra (5 PCs) we're paying $20 a month when the service itself is only about $30 a month. Nearly double just for the IPs. The goal is to use 1 IP and share amongst all connected computers.

So does a router share an IP? If not I might get a 4-port and set it all up as suggested, but use a gateway comp for the cable modem then hook said comp to router via second NIC.

[Stone]

Strange that you do not have the same SUBNET MASK on all PC's.

I assume you have in local area network settings for the TCP/IP set on "obtain an IP address automatically"

If that is the case, your ISP sends very different IP scopes off some strange reason...

Anyway. The subnet mask gets a little complicated, as there are other masks as 0 and 255.

Using the windows calculator (start / run / calc), in (view/scientific) enter the decimal number (eg.255) and then select bin, to see the binary value. Add leading zeros, if the binary number lenght is below 8.

    0 = 00000000
255 = 11111111
254 = 11111110
252 = 11111100
248 = 11111000

Now you have look what IP address you have, and the 1 and 0 has to be the same for all PC's where the there is a 1 in the subnet mask.

Eg.
Subnet 255.255.254.0

The first two numbers has to be exactly the same, and the third nubmer has to be +/- 1 (because the first 7 bits has to be equal, and the value for the last or lower bit is 1)

The fourth number (the last) may be different on all PC's.

So say that your IP address is 195.80.90.5 and subnet mask is 255.255.248.0

In Binary this is:
ADRS 11000011.01010000.01011010.00 000101
MASK 11111111.1111111.11111000.000 00000

For an other PC to be on the same subnet as the one with IP 195.80.90.5 / 255.255.248.0, it has to have an IP address that :

First digit is 195
Second digit is 80
Thirs digit is 88 - 95
  Because 88 = 01011000 and 95 = 01011111
  The netmask 248 alows the three last bits to differ.
Fourth number can be any number.

So in order to see if you computers are on the same subnet, you have to compare the binary IP to the SUBNET MASK.

Even tho you have a different SUBNET MASK on the PC's, they could be on same SUBNET, if the bits are equal on the third value.
(Say if the third digit is the same or +/- 1 on all computers).

I am afraid im not the best person to try to explain this, and this maybe sounds more complicated that it is? (I am not nativ english)

But, in practice, get the router with DHCP and NAT.

Or call the ISP and ask if they can arange their system to send IP config from same SUBNET to all computers. (If they can)

[Stone]

Originally posted by Krusty


However, I've been asked to inquire whether a router shares IPs or if it gives each connection its own IPs?

The router will get a public IP from the ISP, but then all the computers will get non public IP address from the router (assuming the router has DHCP server built in)

So the ISP have no idea how many computers you have

A public address is an unique address on the Internet.
A non public address is only unigue at your home.

Say you configure the router DHCP to give non public adress 10.0.0.1 to 10.0.0.16.

We can not try to ping your PC 10.0.0.1, because it is a non public address, and will not route on the Internet, only on your LAN.

But when you with your 10.0.0.1 PC try to play AH2 or surf the net, trafic will route to the router, that will go to the AH2 server, showing the router IP as your IP.

The router will translate the address back to 10.0.0.1 when the data is sent from the AH2 server back to you. (That is the NAT thing)

But simply put, there can be thousands of PC's with the same non public IP address (eg. 10.0.0.2) but only ONE in the entire Internet with a puplic IP address.

[Kev367th]

Originally posted by Krusty
Naw, I think I get what you're saying. I was thinking I'd have to use the switch anyways, if there's an upstairs/downstairs setup (which there will be). As it is now we have 4 cables running through a hole drilled in the floor. Having just 1 cable (from switch upstairs to router downstairs) would make things a lot eassier.

EDIT: That's an obvious idea you had there, but I totally didn't see it! Getting a 4-port is literally half the price of an 8-port.

However, I've been asked to inquire whether a router shares IPs or if it gives each connection its own IPs? We have cable modem, which gives you 1 IP, but each additional (and they count, trust me) costs an extra $5 a month, and if we have 1 default and 4 extra (5 PCs) we're paying $20 a month when the service itself is only about $30 a month. Nearly double just for the IPs. The goal is to use 1 IP and share amongst all connected computers.

So does a router share an IP? If not I might get a 4-port and set it all up as suggested, but use a gateway comp for the cable modem then hook said comp to router via second NIC.

Yes the router shares the 'internet' connection.

You enter all you stuff given to you by your ISP (IP Address, Netmask, Gateway and DNS) in the WAN settings.

All the home stuff connects to the LAN side, you can choose your own netmask and IP range, or just leave as is.
Enable the DHCP and your off.