IP address problem..

Unanswered Question
Jan 5th, 2009

I have 5 usable IP addresses(static) from my ISP. I want to use 8 devices inside of my LAN. I have linksys for LAN. Give me suggession

1-Should buy cisco router to get 3 more IP address OR

2-Request more IP's from ISP.

What is possible and cheap.

If router is suitable, what model of Cisco and how to set it up.


I have this problem too.
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John Blakley Mon, 01/05/2009 - 12:44

You have 5 public addresses. You probably only need to use one, and then you can use a private addressing scheme on the inside. You wouldn't need to get more addresses.

The private addressing is like:


You would configure NAT, and this translates private IP addresses to public addresses.

You should look at an ASA or Cisco 800 series routers. Depending on what your needs are, either one of these should do fine.



tahir1234 Mon, 01/05/2009 - 13:26

Thanks John for your reply. Because I am not network person so need some clearity on this point. I will allocate one Public IP to my router and then enable NAT on router and then all 8 users will be able to go on internet at the same time. As my understand. On the other hand can I also purchase more IP for my LAN. These are all public IP's and I will have to pay.

Thanks for reply.

John Blakley Mon, 01/05/2009 - 13:34

You should evaluate your options before purchasing a ton of addresses. What services will you be offering to the public? If you're going to be hosting websites for customers, you'd need several public addresses, but if you're going to be hosting servers inside of your office for your own purpose, many times you can NAT the traffic to different servers like:

public IP --> private IP on port 25 (mail server)

public IP --> private IP on port 80 (web server)

public IP --> private IP on port 21 (ftp server)

Private IP is only open on ports 21,25, and 80, which would be a web server. You wouldn't necessarily need many public IP addresses to do this. You can even port forward to different servers, same public IP, but to different internal servers like:

public IP on 80 --> private IP on port 80 (web server)

public IP on 21 --> private IP on port 21 (ftp server)



tahir1234 Tue, 01/06/2009 - 08:06

Thanks John. Can I use Cisco 2600 router for LAN while I have 5 public IP's from my ISP and I am going to use 8 devices (users) in business.


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