Internal & External IP addresses confusions

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2[H]4U
Joined
Jun 12, 2001
Messages
3,887
I am volunteering at a local community center for the elderly & the disabled and they were recently given ten OLD PIV computers

Some of the computers are of the internet and others will not get access even though they are connected to the network (XP Says Limited or no access) as soon as I unplug one computer another one will be able to connect

The ISP is Charter Communications and the account is a business account the modem is an SMC Networks
SMCD3GN-RES and the router is a POS Netgear WiFi G (Which I am going to replace with my extra N router)


Their network is all screwy and I want to fix it for them
They Currently have the two devices I mentioned + a 8 Port unmanged GB switch where the five computers are located (To simplify the ethernet wiring as only one drop is needed)

I think with the business account they have a static IP address and I believe they have access to more then one External IP address (I am unsure but I will get the details if needed)

I am by any means no network expert but I though with a router you only need one External IP Address for all of the computers as that is the main purpose of a router?

Charter is an Evil company and the modem is extremely locked down (I can't even access the setup page 192.168.0.1 or 192.168.100.1 and they had to be called to get all 4 ports active on the SMC Modem)

My main question now is can the ISPs modem limit the amount the Internal IP addresses?

I want to really resolve this problem as cheaply as possible, So every device can access the internet properly

Here is my plan (Please tell me if I am doing something wrong)

1. Get a better N router and another GB switch (All 4 Ports on the Netgear are used and three of them on the SMC modem)

2. Plug the N router into the SMC Modem and then plug the drop from the 8 port switch into the N router and use the rest of the router ports + another switch for the remaining devices

3. ...

4. ??
 
That modem is actually a modem/router combo, as a plus it is DOCSIS 3.0 but the wireless is just draft N and they don't seem to have any firmware updates for it. How is the Netgear router configured? The SMC probably uses DHCP and I imagine the Netgear is using DHCP too which should be turned off.
 
If I'm understanding properly, your current setup is :

Code: 
SMC MODEM/ROUTER/WAP "GATEWAY"
|
└->PC1
|
└->PC2
|
└->PC3
|
└->NETGEAR ROUTER
     └--->PC4
     |
     └--->PC5
     |
     └--->PC6
     |
     └--->SWITCH ------> More PCs

1 - If the Netgear is actually acting as a router, that's not great . The SMC is already a router/WAP/modem ("AIO gateway"), so you have absolutely no need for a second router or WAP (unless you have coverage issues, in which case turn the router into a WAP only). Rule of thumb for anything outside your house or business - wherever reasonable, use the ISP equipment because that is what they have to support. It keeps future problems from falling on your doorstep.

2 - Doubtful they would lock down the number of internal IPs you can get (but anything is possible) - but depending on how the netgear "router" is configured, you could have either 2 networks running, or 2 DHCP servers on the same network. Both aren't great and it should be changed to have 1 network with 1 DHCP server (just the SMC gateway).

First step would be to check the IP addresses that you're getting on all the PCs. They should all be within the same network (for example if it's 192.168.100.x/24 - all computers IP address should start with 192.168.100.)

Depending on the results, you'll have to make your changes accordingly.
 
No... the purpose of router is not to share one external IP with a bunch of internal clients. That is called Network Address Translation and is a function of a router but not what a router is for.

A router is designed to separate broadcast domains from each other, i.e. keep the internet/internal netwoks from being one massive warehouse full of screaming people (computers) where no one would be able to understand one another due to sheer volume of broadcast (noise).

What you need to do is the following...

1. Router, only 1 period (It needs to be DHCP and have NAT enabled). [Remove the 2nd router ABSOLUTE MUST]
2. Use only 1 port in the back of the router and hook a network switch, i.e. a 8 or 16,24,48 port switch into that one port.
3. All computers and printers etc.... plug into the switch.

There ya have it.... the 1-2-3s of how to fix your issues.

I dont think it is that Charter is and EVIL company, it is that you are paying for managed services and with that being said you should NOT have access to their routing equipment even on your end. This is in place to keep people, i.e. yourself who claim to know enough to be dangerous but no enough that you need to come here for help from breaking things worse. How are they able to maintain a high level of service to your building if they allow anyone with a wrench to get in and mess with stuff so to say. Now are they an evil corporation, maybe, but that is for another conversation concerning morals etc... not the fact you are safely locked out of destroying your internet connection even more.
 
Which PCs have issue; the one plugged in to the Netgear, the ones plugged in to the SMC, or all of them?

edit: errr, I was going based on what Innocence presumed your network setup was, but after re-reading for the 4th time, there's only 5 machines, and all 5 are plugged in to a switch, which is plugged in to... what?
I cannot picture the network setup based on the limited info provided on how everything is hooked together.
 
tangoseal said:
1. Router, only 1 period (It needs to be DHCP and have NAT enabled). [Remove the 2nd router ABSOLUTE MUST]
2. Use only 1 port in the back of the router and hook a network switch, i.e. a 8 or 16,24,48 port switch into that one port.
3. All computers and printers etc.... plug into the switch.
Click to expand...

As a person who acknowledges their limitations with network configuration, I think the 1,2,3 steps above will be your easiest / most cost effective solution.

The previous post about setting up your second N-wifi router as an access point to help with wifi coverage is also spot on.
 
Format _C: said:
The switch is plugged into the SMC
Click to expand...

where does the Netgear come in to play?

Also, the machines that are able to get online...
do an ipconfig
What kind of IP address do they get?

Code: 
SMC MODEM/ROUTER/WAP "GATEWAY"
     |
     └--->Netgear
          |
          └--->Switch
               └--->PC1
               └--->PC2
               └--->PC3
               └--->PC4
 
If I had to guess...your modem is set in bridge mode. That has disabled any routing function or dhcp services and is passing through the WAN IP to the first connected device. Make sure that first device is a router, and that all subsequent devices are below that router logically. You may want to check with the ISP as they may have changed this based on your request to "turn on the other ports."

If you just have the switch plugged in, a computer will get an IP but since there is no router with PAT, nobody else can get online. I suspect that your management IP for the modem will be your static WAN IP but only accessible from the single computer that has Internet access.

Long and short of it: either plug the Netgear back in, confirm it is getting the WAN IP, plug all clients/switches into the Netgear Lan ports.

Or have ISP disable bridge mode. Then you can use all the modem ports since it is essentially a switch at that point, plug the Netgear into one of those ports and do exactly what you were trying to do. You can have two routers, it's called double natting. Not pretty but if you need the ports go for it.

Personally I prefer bridge mode.
 
Or call your ISP to come out and set this up for you for a nominal labor fee. They will get it running right the first time and you can breathe easy.
 
Thanks to all that helped me all is well now

I then configured the router to their static
IP address
Subnet mask
Gateway IP address
two DNS Servers

Heres how
I connected everything
So here is my Basic Crude Network map



Code: 
SMC--> Netgear WAN Port --> Netgear Port
1. Computer one

2. Switch 1 (D-link DGS-108)-> 1) Input from the router--> 2-6 for the computers that are for the guests to use

3. Switch 2 (Netgear DS104) ---> 1) Input from router 2) Computer two 3) Smart TV

4. Empty
The community center is very happy every single device is now connected properly and best of all every thing can access the internet
 
Format _C: said:
Thanks to all that helped me all is well now

I then configured the router to their static
IP address
Subnet mask
Gateway IP address
two DNS Servers

Heres how
I connected everything
So here is my Basic Crude Network map



Code: 
SMC--> Netgear WAN Port --> Netgear Port
1. Computer one

2. Switch 1 (D-link DGS-108)-> 1) Input from the router--> 2-6 for the computers that are for the guests to use

3. Switch 2 (Netgear DS104) ---> 1) Input from router 2) Computer two 3) Smart TV

4. Empty
The community center is very happy every single device is now connected properly and best of all every thing can access the internet
Click to expand...
Any logical reason why you're insisting on continuing to use the netgear router, other than an obvious love of useless and redundant network hardware that the ISP won't support?
 
Innocence said:
Any logical reason why you're insisting on continuing to use the netgear router, other than an obvious love of useless and redundant network hardware that the ISP won't support?
Click to expand...
I am using the Netgear as a router as the ISP make them pay to use that modem as a router. (The modem is set to bridge mode) The router is a Wireless 'N' and the old router I replaced, also a Netgear was only a Wireless 'G'
 
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