Provider IP question, how many IP's?

ezbtr

Captain
Joined
May 1, 2002
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If Im set up for one IP address via my one enet port cable modem, can I install a router with a switch, and get multiple IP's for other PC's?
 

Robbabob

Senior Chief Petty Officer
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Jun 5, 2009
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Re: Provider IP question, how many IP's?

If Im set up for one IP address via my one enet port cable modem, can I install a router with a switch, and get multiple IP's for other PC's?

You can do that. The router will take care of allowing multiple devices to access the internet. Best to power them up in order: cable modem, router, and then each other device one at a time.

Good Luck!
 

j_martin

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Sep 22, 2006
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Re: Provider IP question, how many IP's?

If Im set up for one IP address via my one enet port cable modem, can I install a router with a switch, and get multiple IP's for other PC's?

If you want external (routable) addresses your internet provider has to give you the addresses. Once that's done, you can use a programmable router to direct the traffic, or just run the incoming ethernet cable with the several addresses on it to a switch connected to the various routers and servers, each with one of the addresses. I've done this with DSL, never tried it with cable. I asked to set it up on a MIPX circuit once and was told it wasn't feasable.

Normally, the local area network (inside the house) will be on a non-routable subnet such as 192.168.x.x, and the router will use IP masquerading to make all the internal workstations look like the same external IP address. Using magic I'll not try to explain here, it keeps track of all the connections and routes the traffic to the right work station. A non-routable network is also known as the local area network (LAN) or private network. Web routers will not route these addresses.

To connect 2 private networks together through the web, you use a virtual circuit called a Virtual Private Network. (VPN) and walla, it's like you're in the same room.
 

eavega

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Joined
Apr 29, 2008
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Re: Provider IP question, how many IP's?

To connect 2 private networks together through the web, you use a virtual circuit called a Virtual Private Network. (VPN) and walla, it's like you're in the same room.

If you simply need application-level connectivity between two private networks, you can also use port-forwarding, which is a setting in pretty much any router. You can tell your router whenever any traffic moves over a particular port or range of ports, direct the traffic to a particular IP address in your private network. I use this setting to be able to remote desktop to my home computer from anywhere on the internet.

To answer your original question, your ISP will only give you one IP address (usually), but with a router you can create your own network behind the router (most routers already do this with a built in DHCP server). In fact you can create multiple networks within your house with the proper use of subnetting and subnet masking.

Rgds
 
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