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This is a very basic question from a newbie point of view.

I have a dedicated server at Hetzner running Windows 2008 R2.

I bought a subnet of IP addresses to use in this server. They provided me a given range of IPs, incluind one Ip labeled as "Broadcast".

I know how to assign those IPs to the NIC, but should I do something with the Broacast IP, like configure it somewhere on Windows? Or can I just ignore it and I'll be fine?

This IP range will be used to host SSL sites.

pvieira
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  • No, you do not want to assign that IP address. Your network will see that as a broadcast IP address with the IP it is on and the subnet you assign it to. If you assign that IP, you will break stuff. – Nixphoe Jun 29 '11 at 22:19

3 Answers3

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A network is defined by its network address, its subnet mask and its broadcast address.

The network address is the lowest possible address in the network, and it's reserved with the meaning "the network itself, no specific host on it". This is not used for actual communications, but it's important for routing tables. It can't be assigned to a host.

The broadcast address is the highest possible address in the network, and it's reserved with the meaning "all hosts on the network". This also can't be assigned to a host, but unlike the network address, it's actually used for communications, because some protocols need to be able to send messages to all hosts on a network (NetBIOS anyone?).

Simple example:

Network address: 192.168.0.0
Subnet mask: 255.255.255.0
Broadcast address: 192.168.0.255
Usable addresses: from 192.168.0.1 to 192.168.0.254

More complex example:

Network address: 172.16.2.32
Subnet mask: 255.255.255.224
Broadcast address: 172.16.2.63
Usable addresses: from 172.16.2.33 to 172.16.2.62

The network and broadcast addresses are given you for reference, but you don't need to configure them anywhere; both of them can be (and are) computed automatically, given a host's IP address and subnet mask.

All the info you want and many more here: How does IPv4 Subnetting Work?.

Community
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Massimo
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    I was going to post something like an answer, but you just outclassed everyone else. Great post. – Matthew Jun 29 '11 at 23:19
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Do not assign it. A broadcast address is a special part of a subnet that is used to send special messages to all hosts on a given network. You can read more at Wikipedia, they give a nice overview: http://en.wikipedia.org/wiki/Broadcast_address

Honestly, your host shouldn't even be letting you assign that to a host.

BenGC
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In practical use, you can "ignore" the broadcast IP, when it relates to IP assignment against network devices. The broadcast IP is used when a device in the IP network is to "broadcast" to all the devices within that network versus contacting another device in "point-to-point" fashion/mode via the other's specific IP address.

user48838
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