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170 votes
Accepted

Why are IPv4 addresses running out?

The IPv4 Address Shortage According to Vint Cerf (the father of IP), the IPv4 32-bit address size of was chosen arbitrarily. IP was a government/academic collaborative experiment, and the current ...
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87 votes
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Is "IPv10" a joke or a serious RFC draft?

As Ron said, anyone can write a proposal. I have a hard time taking proposals seriously from someone who suggests interconnecting satellites with optical fiber, though. Also, I can't imagine this ...
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82 votes
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Why do we need IPv6?

Two things are getting confused here: classful addressing vs CIDR Masquerading / NAT Going from classful addressing to Classless Inter Domain Routing (CIDR) was an improvement that made the address ...
55 votes
Accepted

Why does the IPv6 header not include a checksum?

One of the ideas around IPv6 was to speed up packet forwarding. To that end, several decisions were made. For example, the IPv6 header was greatly simplified and is a fixed length, unlike the variable ...
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37 votes

Why are IPv4 addresses running out?

Ron Maupin's answer gives a brilliant overview of the IPv4 shortage, but I'd like to address this part of your question: Why can't a city (for example) have just one IP address and all homes in ...
  • 470
31 votes
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Will IPv6 make private IP addresses become obsolete?

No, private addressing will not become obsolete. But actually, there are two kinds of private addresses: the Unique Local Addresses (ULAs) and the link-local addresses (LLAs). There will always be a ...
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28 votes

Is "IPv10" a joke or a serious RFC draft?

You must remember that anyone can submit proposals to the IETF, and they are taken seriously, until they are either adopted or die due to lack of interest. This particular proposal has expired and ...
  • 96.7k
27 votes

Why does the IPv6 header not include a checksum?

Because it's redundant. All the common link-layer protocols, like Ethernet or WiFi, have their own error checking and error correction mechanisms, so physical transmission errors are already unlikely....
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24 votes
Accepted

Why do we need ports with IPv6?

An IP address targets a host on the network layer. Transport layer ports multiplex an L4 protocol within a host (to different processes/services). Both are different things on different layers. ...
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22 votes

Difference between :: and ::1

:: is the unspecified address (0:0:0:0:0:0:0:0), and it is only used in packets as the source address of a host that does not yet have an address and is trying to get an address assigned. What you see ...
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21 votes
Accepted

What is Link-local addressing?

I never seen 169.254/16 working in IPv4. A PC automatically acquires a 169.254.x.x/16 address if it does not receive an IP address from a DHCP server. If you disable the DHCP server on your home or ...
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20 votes

Why is the U/L bit inversed in EUI64?

RFC 4291 provides instructions on how to create the EUI64 address: Links or Nodes with IEEE 802 48-bit MACs [EUI64] defines a method to create an IEEE EUI-64 identifier from an IEEE 48-bit MAC ...
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20 votes

Where can I use the IPv6 documentation prefix

The IPv6 documentation prefix (2001:db8:::/32) must be used ONLY for documentation purposes. It means written examples, diagrams, PPT presentations, Textbook explanations, etc. This range shouldn't ...
  • 4,457
20 votes

How does the shortage of IPv4 public IPs influence existing firewalls?

You're late to the game: IPv4 addresses are already exhausted, and have been for a number of years. All the major manufacturers have included IPv6 capability (in varying degrees) in their product ...
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19 votes
Accepted

What are common sizes to split a /29 - /32 IPv6 subnet?

Some simple guidelines that work most of the time: Dividing your /29 The standard size of your allocation from RIPE NCC is a /32 A /32 is a well-accepted prefix size in the global routing table You ...
19 votes

Is "IPv10" a joke or a serious RFC draft?

Is “IPv10” a joke or a serious RFC draft? Both. That draft doesn't solve a single problem but opens a can of new ones. I guess that bloke is serious and he doesn't get what ridiculous schemes he's ...
  • 76.9k
18 votes
Accepted

What happened to IPv5?

The first four bits in the IP header are used to store the Protocol version (4 or 6). The version 5 was assigned to another protocol, the Internet Steam Protocol and so was not available for the ...
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18 votes
Accepted

What happens when a subnet reaches capacity?

A subnet (network) is really just a collection of contiguous addresses within a binary mask. It is simply a logical way to divide address block. If you run out of addresses in a network (subnet), then ...
  • 96.7k
17 votes
Accepted

Why the first octet of a MAC address always end with a binary 0?

You may notice that two least-significant bits of the most-significant byte of a 48-bit MAC address are usually set to 0 (as in all your examples). There are two flags in the most-significant byte of ...
  • 96.7k
16 votes
Accepted

Stateful vs Stateless IPv6?

Stateful autoconfiguration of IPv6 is the equivalent to the use of DHCP in IPv4. It requires a DHCPv6 service to provide the IPv6 address to the client device and that both client device and server ...
  • 27k
16 votes

Why do we need IPv6?

The Internet Protocol (IP) was designed to provide end-to-end connectivity. The 32 bits of an IPv4 address only allow for about 4.3 billion unique addresses. Then you must subtract a bunch of ...
  • 96.7k
16 votes

Why are IPv4 addresses running out?

Right now, every home has its own IP address. Why can't a city (for example) have just one IP address and all homes in this city would just be on a private network of that city? Exactly this is ...
15 votes
Accepted

IPv6 prefix interpretation

From RFC4291 section 2.3: An IPv6 address prefix is represented by the notation: ipv6-address/prefix-length The whole thing is called prefix. First part up to / is called address. Second part ...
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14 votes
Accepted

Using IP subnet at multiple datacenters

Connect the two DCs with a private connection. Then advertise the /24 at both Data Centers. When traffic arrives at one DC for the other, your internal devices route or switch the traffic as ...
  • 695
14 votes

Could IPv6 make NAT / port numbers redundant?

IPv6 does not have a NAT standard as IPv4 does (NAT breaks the end-to-end premise of IP, and IPv6 was designed to restore that). There is an experimental RFC for IPv6 NAT, but it is a one-to-one NAT ...
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13 votes
Accepted

Why do IPv6 unique local addresses have to have a /48 prefix?

The requirement exists to prevent collisions. This is a bit more important than most people recognize. Even if you have systems which currently don't communicate with other systems over the internet ...
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12 votes
Accepted

How is NAT a hack?

Before NAT every device connected to the internet had its own IP address. That was how the internet was designed. This gives you great flexibility and visibility. If you have a firewall then it can ...
12 votes

Usage of Flow label in IPv6 header?

The above answer isn't really correct. The flow label isn't designed for packet ordering - IP does not care about order, it is an unreliable services whose only goal is delivery on layer3. Better way ...
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12 votes
Accepted

IPv6 and online privacy and security

Let's look at a live example. This being from my Linux workstation. (And for simplicity I actually omitted a couple of addresses.) I'll explain each of the addresses in turn: $ ip a s dev br0 3: br0: &...
12 votes
Accepted

How does router advertisement in IPv6 avoid IP conflict?

A host performs Duplicate Address Detection (DAD) before actually activating the given address on the interface RFC 2462 has to say about this: 5.4. Duplicate Address Detection Duplicate Address ...

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