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Questions tagged [ipv4]

Refers to the 4th revision of the Internet Protocol, where addresses are usually displayed in the form of dotted decimals between 0-255. Ex: 169.254.0.1

The IP address of a device is its unique identifier on a network which allows communication with that device.

Given the fact that only 2^32 IPs are available, number which is already depleted, its successor (IPv6) has officially taken over on 6 June 2012.

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How does IPv4 Subnetting Work?

This is a Canonical Question about IPv4 Subnets. Related: How does IPv6 subnetting work and how does it differ from IPv4 subnetting? How does Subnetting Work, and How do you do it by hand or in your head? Can someone explain both conceptually…
Kyle Brandt
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Why couldn't MAC addresses be used instead of IPv4|6 for networking?

I am reading up on TCP/IP and other related protocols and technologies. MAC addresses are described as being (reasonably :) unique, and as having a large possibility space (several hundred trillions), while also being assigned to all network…
Félix Saparelli
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How bad is IPv4 address exhaustion really?

For years the press has been writing about the problem that there are now very few IPv4 addresses available. But on the other hand, I'm using a server hosting company which gladly gives out public IPv4 addresses for a small amount of money. And my…
oz1cz
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Do you need separate IPv4 and IPv6 listen directives in nginx?

I've seen various config examples for handling dual-stack IPv4 and IPv6 virtual hosts on nginx. Many suggest this pattern: listen 80; listen [::]:80 ipv6only=on; As far as I can see, this achieves exactly the same thing as: listen [::]:80…
Synchro
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What is the rest of the 127.0.0.0/8 address space used for?

We all know what 127.0.0.1 is used for (loopback). What are uses cases for the rest of the reserved 127.0.0.0/8 loopback space?
Tom Marthenal
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What's the maximum number of IPs a DNS A record can have?

I have a strange idea - let multiple people/organizations host the same application, and let all their nodes be accessible via a single domain name. That's in order to have, let's say, a really distributed social network, where usability is not…
Bozho
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Is it valid to have part of an IPv4 address set to zero?

I am working on a change in a Java EE application that would authenticate based on the user's IP address using ServletRequest.getRemoteAddr. We store IP address ranges (FROM_IP and TO_IP) in a database and the system would authenticate only if a…
Ritesh
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Should my website have an IPv6 address?

My website only has an IPv4 address. With IPv6 being the future, is it possible that some users may not be able to reach the website if it does not have an IPv6 address? Also, does having an IPv4/IPv6 address increase SEO performance?
Reado
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What makes a private IP address not routable?

I understand that private addresses such as 10.0.0.0/8,172.16.0.0/12 and 192.168.0.0/16 are not routable. However, what exactly is stopping these addresses from being routable? Do ISPs implement ACLs that prevent these networks from routing or is it…
QuantumRads
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IPv4 CIDR Ranges for Everything except RFC1918

I'm looking for a list of CIDR blocks for "The Internet", i.e. everything from 0.0.0.0 to 223.255.255.255, excluding RFC1918 address space of 10.0.0.0/8, 172.16.0.0/12, and 192.168.0.0/16 (yes, I know there are lots of little nets in there that are…
Jed Daniels
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Is an IPv6-only MTA possible yet?

Has anyone had tried to run an IPv6-only SMTP engine? Pretty much everybody with any sense has IPv6 configured for major front-end servers. I was curious if anyone had tried to run an IPv6-only MTA and received any connection errors. Is IPv6-only a…
joe
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New service decision: IPv6 or IPv4?

While hosting new service these days, what would be best decision. IPv4 or IPv6 ? If we decided to launch it on IPv4 address: How easy/difficult to get IPv4 address (considering they getting exhausted out soon)? Can it be ported easily to IPv6 in…
Atul
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Difference between 0.0.0.0/0 and ::/0 in access control lists

When setting up access control lists, what's the difference between 0.0.0.0/0 and ::/0? I'm seeing this for an AWS EC2 instance I'm setting up
Hassan Baig
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What is the name of an IP prefix with prefix length 31? (i.e. contains only 2 IP addresses)

At my job, IP prefixes with prefix length 31 (i.e. they only fit 2 IP addresses) are commonly described at "linknet addresses". Lately I have noticed that this term doesn't appear to exist outside of my company. If I do a Google search for "linknet…
Hubro
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How to completely, dynamically disable IPv4 stack from Linux?

How can I disable IPv4 stack from Linux ? I want to do that dynamically, i.e. sometimes I want it enabled and sometimes I want only IPv6 stack. Is there any portable way to do that ? If you know how to do that in any distribution, it will also help…
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