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Need unique public IPs from different PCs on a LAN/WLAN

Last response: in Networking
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June 21, 2012 10:30:04 PM

Is this possible?

I have High-Speed cable service, currently using a Cisco 2100 modem. This is currently run into a D-Link DIR-615 Wireless Router which also allows four LAN connections via CAT-5 cable.

I have four or five web-capable PCs in the house, and my goal is to be able to access the Internet with each PC showing a unique public IP address (static is OK). Is this feasible? If so, is there some way for me do do this myself, or something the cable company would have to provide?

I read on another forum that this may be possible by contacting the cable company, and each additional IP addy might cost about $5/month. (And how does THAT work when the connection itself is dynamic?)

Forgive my gross ignorance about networking; that's why I'm here asking questions. Networks and their workings are fairly foreign to me.
a b X LAN
June 21, 2012 11:14:11 PM

You're not going to be able to do this w/ your typical consumer router (well, not unless it allows you to disable NAT entirely, which is probably a bad idea for a home user anyway). It's just not designed to support anything but a single public IP. You either need a router that's specifically designed to support it ($$), or else get yourself a dd-wrt or tomato (third party firmware) compatible router.

http://www.techenclave.com/guides-tutorials/multiple-pu...

P.S. I just did a check of the dd-wrt database, and it's likely your DIR-615 router is compatible!

http://www.dd-wrt.com/site/support/router-database
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June 22, 2012 12:41:56 AM

eibgrad said:
...or else get yourself a dd-wrt or tomato (third party firmware) compatible router.

http://www.techenclave.com/guides-tutorials/multiple-pu...


@eibgrad - Thanks, that looks like it MAY be a good solution for me if I can get someone on the ground here to help me through that process. The only other solution I've seen so far is to purchase multiple routers and remember to change them out for each computer (which, if the goal is to keep public IPs segregated for each machine, would of course disallow using the other computers on THAT router, and also potentially cause each router to get different IPs from the time before, depending on lease expiration settings at the ISP).

I'll see if anyone else has any thoughts, but this one at first blush appears to be a winner!
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June 22, 2012 4:24:56 AM

I'm told this will only work if you obtain a static IP from your ISP, which may or may not be available and will cost a butt-load of money if it is. :(  Any more thoughts? Or do I just buy a pile of cheap routers on eBay?
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a b X LAN
June 22, 2012 11:36:39 AM

Hmm, perhaps you need to make clearer your intentions here because I was assuming you had a clear and obvious reason for having multiple STATIC public IPs, one for each PC. You often see this in business situations when they want individual services that aren't hampered by NAT (network address translation). Or even for individuals who perhaps want to use several online gaming systems from the same location (e.g., 2 or more XBOX Live systems). In most all other cases, a single DYNAMIC public IP is mapped to local IP addresses (e.g., 192.168.1.x) by a NAT router.

So you basically have three options depending upon intent:

1. A single dynamic public IP through a NAT router (most common for home users).
2. Multiple static public IPs through a NAT router (e.g., home user needing unique public IPs for each of their gaming systems).
3. Multiple static public IPs, each w/ its own modem and/or router and no NAT (rare for home user, most likely a business who needs a unique public presence for each system).

Yes, having multiple static public IPs will usually incur additional charges from the ISP (how much varies widely). That’s why the typical home user has a single dynamic public IP, to minimize costs, but at the expense of having to use a NAT router to share it (not always a good thing, esp. if you’re offering services from your network to the greater Internet, or as I said, perhaps a gamer at home).

So what’s your intent here? What’s the problem you’re trying to solve?

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June 22, 2012 3:27:38 PM

eibgrad said:
Yes, having multiple static public IPs will usually incur additional charges from the ISP (how much varies widely). That’s why the typical home user has a single dynamic public IP, to minimize costs, but at the expense of having to use a NAT router to share it (not always a good thing, esp. if you’re offering services from your network to the greater Internet, or as I said, perhaps a gamer at home).

So what’s your intent here? What’s the problem you’re trying to solve?


I suppose the closest one you mentioned would hypothetically be the gaming situation. The intent is to establish multiple selling accounts on one or two 'popular buying/selling venues' for several individuals due to selling limitations on accounts linked via the same IP address. It is not for nefarious purposes, but is quite needful to accomplish legitimate business. We are currently without income & need to QUICKLY liquidate many personal items (own & deceased parent's estate) but are faced with 10-item per month limits :non:  until our two 'real' accounts are aged & established. Obviously would prefer lowest-cost option (single dynamic IP) but would be willing to incur additional cost for a time until limits are removed from main accounts. Each PC/account MUST have a unique public IP which never overlaps with its peers; it would be BEST if the public IPs from each PC were fairly stable, i.e. not constantly changing (but not necessarily static); with a (less expensive existing) dynamic IP through the modem & router from the cable co ISP.

Does this make sense, and if so, which is the best option?

As a possible side issue, you mention "business situations when they want individual services that aren't hampered by NAT." What individual services would be hampered by a NAT router?

Thank you SO much for your help. A local friend simply said, "Ain't gonna happen" but I'm certain there must be a relatively inexpensive way to accomplish our goal; as I said, hopefully the NEED will only be temporary anyway (six to twelve months).

As mentioned, I've read that the 'pile-o'-cheap routers' trick works to accomplish this, as any change in router or NIC with different MAC addy will cause the ISP to assign a new IP for that device, while each subsequent re-use of that same device will likely draw the same public IP again due to same MAC address being stored, provided the lease has not expired for that IP addy. But this approach obviously has its drawbacks, i.e. physically changing out the device for each PC/account AND limiting the use of them to only one PC at a time (at least for THAT website service). I've even read that simply switching Windows user accounts when switching routers will accomplish the same goal, but IMO using multiple segregated PC's is more foolproof (we *have* them so why not use them?)
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Best solution

a b X LAN
June 22, 2012 5:39:40 PM

Seems to me the best approach, both technically and in terms of cost, would be my original suggestion; use a single dd-wrt/tomato compatible router w/ its own DYNAMIC public IP (so you’d still have a normal NAT-based local network behind the router), and then augment that w/ one or more STATIC public IPs that are port forward to those same local PCs. From the perspective of your local network, things wouldn’t appear all that different. You’d still have a bunch of local PCs using the 192.168.1.x network (just as an example), but from the perspective of the internet, each public IP appears unrelated to the other. There’s no easy way for anyone monitoring those public IPs to know they’re ultimately funneled by your ISP back to your one router. And as far as cost, I would assume it’s a lot cheap to buy a block of static public IPs rather than establish additional accounts, one for each dynamic public IP, and probably additional modems, routers, etc. But that’s an assumption, only asking your ISP will give you the hard numbers.

Btw, I would probably mention to the ISP that you only need these temporarily. Some ISPs can be quite flexible and willing to work w/ you to solve specific problems. They may offer discounts if you buy a block of IPs, say in groups of 4, 8, 16, whatever you need, and esp. if they know they will shortly get them back! What makes this a premium feature is that the pool of available IPv4 addresses is limited, and so once they allocate them, they're unavailable to anyone else until you relinquish them. But who knows, maybe the ISP would offer a discount for a limited time use.

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June 23, 2012 1:41:46 AM

Best answer selected by BackInBlack.
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