# Multiple Static IP's running through a single router.



## dannyelectron (May 18, 2009)

Hey everyone, new to the site and would appreciate if someone can help me figure this out as hours of research has got me no where.

I got a block of 5 public static IP's from my ISP and ultimately I would like to use 4 of the static IP's to be used as 1 static IP per individual computer on 4 of them and the 5th static IP to be shared by DHCP for the rest of the computers in the office (about 10 computers). Doing so, I need all computers to still be on the same network. I have accomplished getting the router to accept 1 static IP and all the computers are using that same static IP but I am not able to configure it for the other 4 computers to use the different IP. I was told what I need to do is go into Windows on the 4 computers and set tcp/ip properties to manually configure the IP and DNS settings.

1. The IP being something outside the range of DHCP server.. which I have done.
2. The subnet mask and default gateway of the router which I have set.
3. The DNS server provided by my ISP.

After setting those properties on the computer, the internet still works however the public IP is still the same IP as the rest of the them. (the static IP set from the router and I need it to use one of the different IP's)

How do I tell the router that this internal IP (192.168.2.1 for example) to give it its own public IP to the internet.

I hope I wasn't being too confusing in my description and any help would be appreciated. The ISP provided a Modem and a mandatory 4 port router that you must use in order to use the static IPs. Aside from that, my other equipment includes a 16 port switch, a WRT54GL Linksys router with Tomato firmware, and a WRT110 Linsys router (stock firmware). I got the WRT54GL router because I thought Tomato might help me out with this situation. 

Thanks in advance.


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## johnwill (Sep 26, 2002)

I know that DD-WRT handles it, here is a couple of many threads on setting it up.

http://www.techenclave.com/guides-and-tutorials/multiple-public-ips-one-router-using-100375.html

http://www.dd-wrt.com/phpBB2/viewtopic.php?p=66001


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## dannyelectron (May 18, 2009)

johnwill said:


> I know that DD-WRT handles it, here is a couple of many threads on setting it up.
> 
> http://www.techenclave.com/guides-and-tutorials/multiple-public-ips-one-router-using-100375.html
> 
> http://www.dd-wrt.com/phpBB2/viewtopic.php?p=66001


this is EXACTLY what I needed. I haven't tried it yet since I'm not at the office but thank you so much for your help. I will change the tomato firmware to DD-WRT  Thanks again and I will keep you posted on my results.


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## dannyelectron (May 18, 2009)

Before I change to DD-WRT, anyone have a guide like this that works for Tomato? If not then I will just change to DD-WRT.


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## johnwill (Sep 26, 2002)

I'd check in their forums and see if they have that support. I did a quick search and turned up nothing.


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## dannyelectron (May 18, 2009)

awesome! got it working within 15 minutes with your guide provided for DD-WRT. thanks for all your help.


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## johnwill (Sep 26, 2002)

Glad it all worked out. Sometimes things do work out. :grin:


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## dannyelectron (May 18, 2009)

Hello again,

Bringing up an old topic because office likes to drive me crazy.

Got an issue , the place I did this for had 1 modem with 5 static IPs. Their provider would not offer them more static IP's with the same modem so they just bought another block of 5 IP's with another cable modem.

How would you go about this installation for the 10 IP's (preferably having all the computers still networked)

Is this even possible to have them all networked or would I just need to do this twice on two different routers and they will not be networked?

Thanks,
Danny


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## Suncoast (Jul 28, 2009)

It's a shame they wouldn't give you a /28 block, you would have received an extra 2 IP addresses, and it would have made things much simpler. 

Because you're using static IP addresses inside, you should be able to do this. Simply point the 5 new static IP's default gateway to the new cable modem. But without some careful configuration, clients on the old IP's and clients on the new IP's may end up going through the cable network to talk to each other. So you would need some static route commands on your DD-WRT loaded routers. 

Because this is really a Linux question, I think I'm going to point you to the home forum for DD-WRT which is here.
And you may want to look at this Linux Networking forum at LinuxQuestions.org  as well.


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## dannyelectron (May 18, 2009)

I've been doing some research that I wanted to run by you. It may not be the most advanced way of doing things but I think it would work by what I've been reading...

The current connection I have is Cable Modem --> IP Device --> Router --> Switch.

The switch handles 4 static IP's and shares the 5th static IP between all the rest of the computers.

If I run this exact setup on the new cable modem for the 5 static IP's giving 5 PC's static IP's through a switch again by having this setup identical to the previous one but completely separate connection. This would give us the result we want except they will not be networked. Then in order to network them I would run a crossover cable between the switch connected to one router to the switch of the other router. 

Would this work?

Thanks for your help.


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## Suncoast (Jul 28, 2009)

That would depend. You would need to account for all the IP subnets on all devices. So lets say you setup your existing network as (Using simple classful networks) 

200.20.30.0 255.255.255.0 

This means your network is 200.20.30 and you have 254 host IP's. Now say you added network 200.20.31.0. 255.255.255.0 Your network ID is unique, but your host ID's are not. 

For example, to the local network, the IP address of 200.20.30.1 would be the same as 200.20.31.1. The host ID's (without the network ID) must be unique on the local area network (LAN.) Best pratice says they should be unique for each LAN Segment. The Netmask determines what part of an IP address is Network and what part is host. 

So you COULD, for example, on the same LAN, run Networks 200.20.30.8 255.255.255.248 and 200.20.30.16 255.255.255.248, No duplicate hosts ID's. Both networks would likely have a default gateway of 200.20.30.1, which is the ISP. However, how do you keep traffic from 200.20.30.8/29 to 200.20.30.16/29 from routing across the cable provider? Well, you can't prevent it without breaking out iptables. But you could add a route statements on your Linux routers to route those networks internally on the LAN, and default route out the network for the balance of the traffic. But how will the traffic travel having the same default gateway? These are issues I am not sure of with DD-WRT. That's why I pointed you to the other forums.

Now I've said all this on the assumption that your routers only support one WAN ethernet port each, the port that connects to the cable modem, and that there is no budget for a real hardware router with 4 ethernet ports. Because then you're talking about a much more conventional method for doing this. Or if you have a switch that supports VLANS, you could do it with a router that has 1 ethernet port using a method called "Router on a Stick." Or you could do this by setting up a PC running Linux Slackware or similar distribution. But if you are not already familiar with Linux, this would not be a good starter project.


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## dannyelectron (May 18, 2009)

Wow you lost me big time lol. Little too advanced for my knowledge. 

What if I turned off DHCP on the second router since I will be only using it for 5 static IP's, that way it shouldn't interfere with the other router would it?

Please excuse the ignorance, I'm decent with computers but not advanced networking.


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## Suncoast (Jul 28, 2009)

Before I go any further, could you please explain why you need more static IP addresses? Because the solution may be to better use the 5 IP's you already have. And I would also like to know if the computers in your office need to talk to each other. 

Steve


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## dannyelectron (May 18, 2009)

The reason for the multiple IP's is that its a real estate office and they post on craigslist. So more IP's going to craigslist allows more posting for each agent without getting the account killed. Also if an account gets killed, it doesn't destroy the others. 

They don't NEED to be networked but it would be preferred for sharing printing purposes and file sharing (not as important as printer sharing)


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## Suncoast (Jul 28, 2009)

Ok, I see the need. Have you looked at TOR? Check out http://www.torproject.org/

Now I need to know a few more things I should have asked in my last post. 

What are the 2 blocks of IP addresses? Please confirm the first 2 numbers of both addresses are the same numbers (do not publicly post them) then zero them out. (Example I need 0.0.12.8/29) 

Are both IP subnets provided by the same Cable provider? 

What is the model number and brand of your existing router? Which release of DD-WRT is it running? 

In case you need to get a fast answer, connect the 5 people that need static IP's directly to the new cable modem with an 8 port switch for now. Do not cross connect anything between these 5 and your existing network yet. These people may need their own printer setup on one of the computers as a shared printer.


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