IPv4 vs IPv6: The Key Differences Explained

We all know that we are running out of IPv4 addresses. Therefore, the IETF developed Internet Protocol version 6.  To accommodate the growing worldwide demand, this new generation of IP has a significantly bigger address capacity than IPv4. However, there are many more differences between the two Internet Protocol Versions.

Let’s check out the key differences between IPv4 and IPv6 addresses!

Address Capacity

One of the major differences between IPv5 and IPv6 is their address capacity. IPv6 supports more than 340 undecillion addresses, whilst IPv4 only supports around 4.3 billion addresses. This is due to the address size:

  • IPv4 is a 32-bit IP address
  • IPv6 is a 128-bit IP address

Number of header fields

IPv4 offers 12 header fields whereas IPv6 offers 8 header fields. 

What they look like

  • IPv4 is a numeric address that uses the dot-decimal notation (.). For example:
  • IPv6 is alphanumeric. Its binary bits are separated by a colon (:). For example: IPv6:  2a0e:5540::53 (short version) 2001:0db8:85a3:0000:1319:8a2e:0370:7344 (long version)

Packet size

  • IPv4 requires 576 bytes with optional fragmentation
  • IPv6 requires 1280 bytes without fragmentation

Type of Addresses

IPv4 supports broadcast whereas IPv6 doesn’t support broadcast.

  • IPv4 supports unicast, broadcast, and multicast
  • IPv6 supports unicast, multicast, and anycast.


  • IPv4 was not designed with security as a priority. Therefore security is dependent on applications.
  • IPv6 has IPSec (Internet Protocol Security) build-in. It is usable with the proper infrastructure.


  • For IPv4, the Internet Protocol Security (IPsec) is optional.
  • With IPv6 IPsec support is a required option.

Network Configuration

One big difference between IPv4 and IPv6 is the technology related to network configuration. Manual configuration or Dynamic Host Configuration Protocol (DHCP) is used when a computer tries to connect to the internet via IPv4. However, IPv6 supports autoconfiguration capabilities. It does not require manual configuration or DHCP.

VLSM support

  • IPv4 supports Virtual Length Subnet Mask (VLSM).
  • IPv6 doesn’t support VLSM.

Address Resolution Protocol

  • Address Resolution Protocol (ARP) is available to map IPv4 addresses to MAC addresses.
  • Address Resolution Protocol (ARP) is replaced with a function of the Neighbor Discovery Protocol (NDP).

Mapping hostnames

  • With IPv4, host address (A) resource records in the Domain Name System (DNS) are used to map hostnames to IPv4 addresses.
  • With IPv6, host address (AAAA) resource records in the Domain Name System (DNS) are used to map hostnames to IPv6 addresses.

Pointer resource methods

  • With IPv4, pointer (PTR) resource records in the IN-ADDR. ARPA DNS domain is used to map IPv4 addresses to host names.
  • With IPv6, pointer (PTR) resource records in the IP6.INT DNS domain is used to map IPv6 addresses to hostnames.


  • In the case of IPv4, fragmentation is performed by both Sender and Forwarding routers.
  • In the case of IPv6, the fragmentation is performed only by sender routers.


Both IPv4 and IPv6 are two major internet protocols. In the future, a movement from IPv4 to IPv6 is inevitable. IPv6 does not only provide more addresses to meet the internet demand, but also simplifies network operation. However, this doesn’t mean that IPv4 will go away any time soon.

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