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I would like top know if I need 5 public IPs on my network ( 1for my asp application, 1 for the Modem, 1 for the Router and 2 for the Security Firewall)?

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closed as too localized by slhck♦, MaQleod, random♦ Jul 12 '12 at 4:28

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You should clarify but if I understand you correctly, no. You will need one public ip address that your modem will use. Your router can provide you with private addresses (NAT) for your internal devices.

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actually i have an web-base application that i want to host locally but allow people to access. i have a router, a firewall and and my server. some told me that i need 4 public IP for each device and one for my application. i don't understand why 5. i have basic Knowledge in networking – Sept Jul 11 '12 at 18:31
@Sept : each device? is this just a computer on your local network? You really only need 1 public IP unless you want redundancy or you do not want to share bandwidth. Static IP would be best, and all you need is a Domain Name and point it towards your IP... and use your router to forward the request to the proper computer that hosts your web application/site. – Logman Jul 11 '12 at 18:45
You will only need one public IP address. You will need to set up port forwarding on your router and configure your firewall to allow traffic destined for you server. There are many write-ups about this but you will need to find one specific to your devices. – user142485 Jul 11 '12 at 18:45
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If you use 1 IP address, then you will need to use different port numbers, otherwise the router will have no way to distinguish which device on the inside to send the traffic. Alternatively, you could set up a reverse proxy like nginx and configure unique URLs that are proxied to the different servers on the inside based on the URL.

Personally, I would use 2 IP addresses if that is an option, one for the modem and ASP application, and one for a VPN device. You should use the VPN to manage the router and security firewall, otherwise those devices are exposed to the internet for botnets and the like to try to hack them 24/7, and they will try. A VPN is usually less hackable provided that you use a certificate or strong pre-shared key.

For some services, like SIP and XMPP (Jabber) but not HTTP nor HTTPS, you can use a DNS SRV record to specify a different port number and most clients will recognize it, this is specified in RFC 2782. Web browsers have not implemented this behavior although it has been filed as a bug against Mozilla since 1999. Based on reading the bug comments it seems that the problem is that parts of libraries would have to be rewritten to allow for this change and that has been a barrier to implementation.

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