Why multiple IP Addresses on NIC ?


I am sure this is a dummy question but i suck in networking.

What is the purpose of a windows server box to have multiple ID addresses assigned to it, although they share the same host-name on DNS?

Thanks 4 your help,
namergSystems AdministratorAsked:
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Bill BachPresident and Btrieve GuruCommented:
For a standard workstation, there is little value here.  However, it is certainly possible to run multiple network address ranges on a single set of cabling (though this can get REAL confusing, so we don't recommend it).  Further, you can have multiple NIC's assigned on the SAME network segment for fault tolerance purposes.  Multiple IP addresses can also be used for servers in a cluster (each server has its own IP address, but the one with the cluster resource mounted gets the cluster IP address) and for some replication solutions for fail-over and fail-back capabilities.

If you gave a better description (i.e. what addresses are assigned), then we might be able to help narrow this down.
namergSystems AdministratorAuthor Commented:
Okay, I will. Happy Holidays.
Tom CieslikIT EngineerCommented:
Let say you're providing  internet services like website for different companies and you want them access their website.
You need to create rules on your firewall to forward request for only one port like 80 or 443
So you need to create many DNS Lookup ZOnes for many website/domain addresses and forward request to you IIS server.

So let say in clients Public DNS all www requests will go to same A record under same IP (your company) you must forward request to different local IP's on Your IIS server inside your network, that's why you're adding more than one internal IP on IPv4 properties of your server NIC to make this work and configure each website on same server to work/respond on different IP.

Some time ago Microsoft had product called Microsoft ISA server
This was a Programmable firewall so you could create any rules and port forwarding
To do this you had to assign external IP address for your client on one NIC and internal IP on second. Tis way you was able to create port/request forwarding for many clients to your local internet resources.

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Shaun VermaakTechnical SpecialistCommented:
Used during migration to map old server IP to a new server in case developers hardcoded IP address somewhere.
Also, you can give a device two or more hostnames too using the NETDOM command for the same reason.
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