IP Addresses from other ISPs

I have a few static IP Addresses I pay monthly for from my DSL ISP. I run web servers on the IP Addresses, and do some hosting for a couple small sites. The ISP charges me $10 a month per IP Address, and they do not offer any package plan. So that kinda sucks.

Well, the other day my friend mentioned he needed web space and wanted to know if he could pay for a static IP Address for us to host. Then he asked if he bought an IP Address from another ISP, if he could just use that one on our servers. He insisted that it is easy to do and wouldn't require reconfiguring our network at all. That comment confused me. I have never done anything like that, nor have any clue how I would go about setting that up on the servers.

Is that even possible? Purchasing IP Addresses from another ISP, and have a server using not only the assigned IP Addresses from it's own ISP, but also using other IP Addresses bought from a different provider? If that is possible, I am thinking about finding a place that would sell IP Addresses for cheaper than the $10 / month now I get charged. But I have never heard of doing that, and am wondering if it is even possible.

Any info appreciated. Thanks.

try calling your ISP prodiver and see what they say. I think you can cause its just an IP. But I am not sure.

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Originally posted here by casper3699
try calling your ISP prodiver and see what they say. I think you can cause its just an IP. But I am not sure.

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That's the thing, if I call my ISP they'll say "Yea we'll sell you an additional IP for $10 a month". They aren't going to point me in the direction where I can purchase cheaper IP Addresses, and then tell me how to do it.

I still don't understand how this would be possible. Being on one ISP, but using IP Addresses from another. I figured that technically you are on your upstreams network, so you could only use the IP addresses for that network. Can anyone shed some light on how this would work?

I would say it would be possible to have a machine that did it, but it would require that you had connections to both ISP's. If you can't get a connection to both, I don't see how that would be possible. Think about it, if you just arbitrarily changed your IP to be in Microsoft's network range, would it work ? Nope...Now, depending on how your ISP is setup and how you setup your end, the traffic might make it to microsoft (assuming your ISP doesn't do any ingress/egress filtering); however, the traffic would never return to you because either Microsoft would outright kill it at their boundary devices with ingress/egress filtering, our their routing would send the reply either into a routing loop if the network didn't exist, woudl reset the connection if the network/host did exist, or would time out if the network existed and not the IP...

Neb

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Originally posted here by nebulus200
I would say it would be possible to have a machine that did it, but it would require that you had connections to both ISP's.

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That's how I am looking at it. That's why my friend's comment confused me so much. I know if I had a connection the the ISP I could get an IP Address from them. But he is saying that all I have to do is purchase the IP and do something simple to assign it to the machine. He started going into DNS babble, which really confused me because DNS doesn't assign IP addresses to networks, only Domain Names to IP Addresses (as far as i know).

The problem I am running into here is that the only high speed available in my area is DSL. There is no way I could afford a T1 or higher. And the only ISP that offers DSL in my area charges $10/month per IP Address. That $10 is starting to add up. I see all these other providers giving out up to 8 IP Addresses for $20 a month. That would save us some major money.

I have a feeling he is getting confused about moving your domain/site name to a different ISP. That is in fact trivial and easily done. Now if you wanted to switch ISP's, you could do that, move your domain over, and save the money, but your IP will change...(which to the rest of the world really won't matter since they use your sites name and not IP, and a change of domain/DNS will fix that).

Neb

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Originally posted here by nebulus200
I have a feeling he is getting confused about moving your domain/site name to a different ISP. That is in fact trivial and easily done. Now if you wanted to switch ISP's, you could do that, move your domain over, and save the money, but your IP will change...(which to the rest of the world really won't matter since they use your sites name and not IP, and a change of domain/DNS will fix that).

Neb

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Yea, I think he is confused. I wrote him an e-mail asking for more details before it drives me insane. I wouldn't mind switching ISPs and you are right all I would have to do is update some DNS entries. But the only other high speed access available around here would be to get a t1 line. I definitely can't afford that right now. And there is only 1 DSL provider in the area, and thats the one I use that charges the $10/month per IP.

Oh well. Thanks for the info.

you cannot use connection for both isp's since each isp got it's ip block and cannot transfer ip, it's routing issue.

The basic premises on IP is that is it a 32 bit hierarchical address space. Each of the ISP out there has blocks of IP addresses they purchased from some other provider or ARIN if they are a back-bone provider. As you are aware it is the network potion of the IP address that allows for routing to take place. Hence you can not have conflicting address residing on the same network. It is the basic premises of IP routing. You can have IP forwarding. If he has an IP address purchased from and ISP and they will forward all requests to that IP address to another (your private address) this maybe what he is talking about, but this is more likely reference with domain name forwarding. Anyway the point being you can not have IP different IP address residing on the same network. It violates the entire premises of IP

NO it will not work.

Many of the other posts here have touch on a lot of good points, but I didn't see one that is exactly right, so hopefully I can clear it up for you.

If you have an IP from another ISP, there would be no routes on the Internet that would point to the IP address. Your ISP simply has routes to their address space within their network, which would include you because you are part of thier network.

Now...it is technically possible, but your ISP would have to advertise the IP address in it BGP route advertisements or have a static route to the box. Also, it would require that the other ISP would remove any route advertisements it had for the that subnet so that there are not to routes to the same subnet. Like I said, it is technically possible, but the ISP's will never agree to do it and it would be alot of work, so don't even bother trying.

It would be similar to the same method used if you bought your own public address space from ARIN. The ISP would just have to advertise the route to your network for you. This is done quite often for many companies who have their own address space, but for someone who just wants a single IP routed through a separate AS, you got no chance...

Try a hosting provider or pay the $10...