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Hey guys, I know this is a noob question, but I'm having trouble finding a simple, clear answer:

In a default install of MS Server 2003, what defines how many IP address you have available for websites?

For example, in my install, when I go to create a new website, there's only one IP address. But at work, IIS has multiple IP address.

Why, and what defines them? and how do I get more?




Is response to Dave's answer below:

What does "Bound to the system" mean. Whats the overhead of binding more? At what level of the infrastructure is it bound?

If I were to ask my hosting company to give me more IPs, what am I really asking for?

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up vote 2 down vote accepted

The number of IPs available in IIS is the number of IPs that are bound to the system. To see your IP information run ipconfig /all from the command line:

C:\>ipconfig /all

Windows IP Configuration

        Host Name . . . . . . . . . . . . : host1
        Primary Dns Suffix  . . . . . . . :
        Node Type . . . . . . . . . . . . : Unknown
        IP Routing Enabled. . . . . . . . : No
        WINS Proxy Enabled. . . . . . . . : No
        DNS Suffix Search List. . . . . . : home

Ethernet adapter Local Area Connection:

        Media State . . . . . . . . . . . : Media disconnected
        Description . . . . . . . . . . . : Broadcom NetLink (TM) Gigabit Etheret
        Physical Address. . . . . . . . . : 00-1A-4B-74-C3-34

Ethernet adapter Wireless Network Connection:

        Connection-specific DNS Suffix  . : home
        Description . . . . . . . . . . . : Broadcom 4321AG 
        Physical Address. . . . . . . . . : 00-1A-73-85-FE-43
        Dhcp Enabled. . . . . . . . . . . : Yes
        Autoconfiguration Enabled . . . . : Yes
        IP Address. . . . . . . . . . . . :
        Subnet Mask . . . . . . . . . . . :
        IP Address. . . . . . . . . . . . :
        Subnet Mask . . . . . . . . . . . :
        IP Address. . . . . . . . . . . . :
        Subnet Mask . . . . . . . . . . . :
        Default Gateway . . . . . . . . . :
        DHCP Server . . . . . . . . . . . :
        DNS Servers . . . . . . . . . . . :
        Lease Obtained. . . . . . . . . . : Monday, June 22, 2009 10:44:40 PM
        Lease Expires . . . . . . . . . . : Tuesday, June 23, 2009 10:44:40 PM

To get more IPs you will need to be able to bind them to the system. Most home routers will allow you to add additional IPs beyond the one that is usually assigned by DHCP. You just need to manually specify the list of IPs. Just make sure to choose one outside of the range that gets automatically assigned.

This answer assumes you want additional IPs for internal use. If you need more world-facing IPs you will need to contact your ISP and purchase them. Is there a reason that you need multiple IPs?

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thanks dave. So, what does "Bound to the system" mean. Whats the overhead of binding more? At what level of the infrastructure is it bound? If I were to ask my hosting company to give me more IPs, what am I really asking for? – andy Jun 23 '09 at 3:59
Well I'm assuming that your home computer is behind a router/firewall combo so the IPs that your system listens on (the bound IPs) are internal. The public IP is assigned by your ISP to your router/modem and web traffic would have to be forwarded to your system's internal IP. Most ISPs won't allow traffic on port 80 anyway unless you have a package that explicitly allows hosting. – Dave Forgac Jun 23 '09 at 4:06
If you're talking about running this off your consumer ISP then you'll have two issues. One they tend to block port 80. Secondly they treat your connection as a host connection so you only get 1 IP address. Business class services assign your connection a route which has a subnet which you'll need to route to the traffic to each IP to the proper computer within your network. – 3dinfluence Jun 23 '09 at 4:20

IIS uses any IPs added to the system to answer requests. The default setting of the default website in IIS is "All unassigned". When you add additional IPs to the server you can choose to bind one or more of those IP's to any particular website(under website properties-web site). You can also bind sites to the same IP but on different ports. the default web port is port 80. IIS also has the ability to serve site up based on the host header (domain name). You would really only need to ask your hosting provider for more IPs if you had a reason to have additional IPs alocated to the system. While there is no real overhead for additional IPs on the system, you would only need to dedicate an IP if you had a high traffic site, or a reason for that domain to have it's own IPs (eg if each domain had it's own mailserver you'd probably already have web site IPs allocated as well)

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What dave said... and to address some of your edits, you're just asking to rent an asset, basically.

Your ISP bought (leased? rented?) a large block of IP addresses and will rent you the use of one or more of them for as long as you pay the fee. The address is unique in the world, and only your ISP is intended to use it.

Nothing's physically stopping you from just making up an IP address and attempting to use it, but by getting a legitimate IP, you're ensuring that no other (legitimate) host will be using the same IP.

As to where that address is configured, it's likely set as a static IP on a physical NIC on your host, though you'll likely have various rules in your firewall to ensure that only the desired kinds of traffic make their way to that machine.

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To address one of your edits, binding the IP address means that, once you've been given permission to use it (from your ISP, etc.), you need to add it to your NIC. Go in to the TCP/IP properties for the NIC you need to add the IP too, under the Advanced button, and add the new IP and subnet mask. Click OK/Apply the whole way back out.

Once that's done you should be able to bind one or more IIS sites to the new IP address through the IIS Manager.

As an alternative you can use port or name based hosting in IIS as well. Port based isn't as nice because you can't have two sites using the standard HTTP port (port 80). Name based is doable, you add host header values to you various sites, and, as traffic comes in on one IP IIS will inspect the headers and send it to the correct site based on the name provided. That's useful if IPs are scarce or simpl not available or affordable.

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I assume you already know where to set the IP addresses in ISS; but for the sake of the next guy, you can do it here:

  • IIS Manager->SERVER->Web Sites->[Web Site Name]->Properties->Web Site(Tab)->Web site identification->Advanced(button)

However, I'm curious as to why you want to have multiple IP addresses. I don't see much benefit to having multiple IPs pointing at one particular web site.

If you are trying to run multiple websites on one server, you generally don't need multiple IPs. You can share one IP amongst multiple sites (unless your website requires SSL).

Also, if you really do require multiple IPs for your project, remember that multiple IPs can be assigned to a single NIC. That should save you some hardware and down time.

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