Internal & External IP addresses confusions

[ComputerWizKid]

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. ??

 

[lif_andi]

A likely cause of your limited amount of simultenous connections to the network might be the DHCP scope from your router. As you say, when one disconnects, other can connect, so if the scope is limited to say 5 computers, then only 5 computer can have active connections and the rest will wait. If this is the case, this is something you should be able to change to allow more computers on the network. Alternitively, you could assign static addresses to selected computers and they should connect just fine, regardless of DHCP. Just make sure they are on the same subnet, like if the computers are on 192.168.1.x with a subnet mask of 255.255.255.0 then make sure your static addresses are configured within this same subnet, and that your static addresses don't conflict with those within the scope of the DHCP. Don't know how advanced your knowledge is so if any of this doesn't make sense just say so and we work it out.

If your computers are using the router for acquiring IP addresses, and not the modem, then your problem is not modem related and all is good. If cheap is all you're after and only senior citizens are using the computers, then an extra gigabit switch is not really required, since 100Mbps is more than enough for almost all grannies and grandpas 🙂 So you might save a few bucks there, although I think Gb can be had pretty cheaply nowadays. Also a G router should be enough for all internet connectivity purposes, so even there you don't need to upgrade. If people are using the local network on the other hand, N devices would speed things up nicely (as long as you have N capable computers).

If you're paying all this out of your own pocket then what you do just depends on you, and how much you're willing to spend. If they are paying and have a very limited budget, then you can really save on just using the same devices and try configure them more efficiently.

Good things to know would be your internal IP address range and subnet information, and if you actually have more than one external IP address. Seeing how the number of devices seems rather limited, I don't see the need for that to be the case. Also good to know is how the network is used, is there work related traffic, as in the carers needing connectivity outside, and if its only to the internet or some server somewhere where they need to access files.

Seeing as this is for a good cause and all, I am more than willing to help, and although I am no expert, I am CCNA and starting to get into things, so I can offer some help. Some other guys here though are majorly overqualified and might also be willing to help with things, so you'd be better off listening to them, but as I say, I will pitch in when I can and with the simple things.

EDIT: Also make sure that the IP address you are using is the one to your modem. Common numbers are 192.168.1.1 and 192.168.1.254 but this could have changed or is just different for your modem. Ping the address you think is the right one, and if you get replies then you should have found it.

 

[ComputerWizKid]

I was actually going to give them my extra 'N' Router + an extra 10/100 Switch I had laying around doing nothing
I know nothing about subnetting
I am just trying to get everything working with what I know (And the hardware I have)

There is no server but there are about 4 work computers on the network with the five computers + a smart flat screen TV
The current 'G' device is also setup for WiFi for people that want to bring their own laptop or other WiFi device

 

[thirdeye]

Are you able to access the Netgear device's management? I'd be curious to know which device is assigning IP addresses to the clients. Whether the modem/gateway is giving out IPs or if the Netgear device is (or god forbid both which would also cause issues).

I think lif_andi is on the right track with the DHCP scope possibly being limited or perhaps causing an issue. Can you verify that the devices that aren't able to connect to the internet have valid IP addresses? They would most likely be in the same subnet as a working device and I'm guessing it would be in the 192.168.x.x range. If it's a 169.x.x.x IP it's not getting DHCP info from either device that could potentially provide DHCP on the network.

 

[ComputerWizKid]

Are you able to access the Netgear device's management? I'd be curious to know which device is assigning IP addresses to the clients. Whether the modem/gateway is giving out IPs or if the Netgear device is (or god forbid both which would also cause issues).

I think lif_andi is on the right track with the DHCP scope possibly being limited or perhaps causing an issue. Can you verify that the devices that aren't able to connect to the internet have valid IP addresses? They would most likely be in the same subnet as a working device and I'm guessing it would be in the 192.168.x.x range. If it's a 169.x.x.x IP it's not getting DHCP info from either device that could potentially provide DHCP on the network.

OK I accessed the Netgear router and both the modem and 'G' device are assigning addresses by DHCP. The computers that can't access the internet do infact have a 169.x.x.x address

 

[thirdeye]

Ok, well then problem #1 has been found. Two DHCP servers on the network will only cause issues in this instance. If it were me, I'd disable DHCP on the modem and make sure that the Netgear is serving a DHCP scope/range sufficient for all the devices on the network.

You should then only be using 1 port on the modem which should be connected to the WAN port on the Netgear. Everything else (switches, computers, etc) should be connected back to the Netgear either directly or via a switch. Once that happens everything should be getting a DHCP address in the same subnet from your Netgear. From there you'll just need to make sure that the Netgear is configured properly to work with your ISP. Usually simply connecting it to the WAN port will suffice but that's not always the case.

 

[lif_andi]

If you have work computers and also some sort of guest access to your network, you might want to take a little time to find out what kind of security would be suitable. Having random people access a network that is connected to perhaps sensitive workstation data might not be the best idea. If I have some time this weekend I will try to look into what your devices are cabaple off and maybe suggest 1 or 2 things. But overall I think we're on the right track. 🙂

Like thirdeye says, keeping things simple on your modem is a good idea, and then you can do configuration on the router. That way there is only one place you need to access to make changes and configurations and you're on your way to making a better and more efficient network.

 

[ComputerWizKid]

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
Here is my Basic Crude Network map🙂

Heres how
I connected everything

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