Time to read: 2 minutes, 43 seconds | Published: October 28, 2025
IPv4 and IPv6 What are IPv4 and IPv6?
IPv6 (IP version 6), defined in RFC 2460, is the most recent generation of the Internet Protocol (IP) defined by the Internet Engineering Task Force (IETF). IPv4 (IP version 4) was the first stable version of Internet Protocol (IP). IPv6 is intended to eventually replace IPv4, but now they are tightly mingled and most engineers run them together.
What are the benefits of IPv6?
The IP layer of the TCP/IP protocol stack is the most crucial piece of the whole Internet architecture. However, the limitations of IPv4 in terms of scalability and capability became obvious within ten years of IP going mainstream in the 1980s. IPv4 requires several add-ons like ICMP and ARP to function and by the mid-1990s, a replacement scheme was developed to accommodate exploding Internet requirements. It’s important to note the Internet technology profile that mandates access via IPv4 and access via IPv6 have to coexist.
IPv6 offers these improvements over IPv4:
- More efficient routing without fragmenting packets.
- Built-in Quality of Service (QoS) that distinguishes delay-sensitive packets.
- Elimination of NAT to extend address space from 32 to 128 bits.
- Network layer security built-in (IPsec).
- Stateless address auto-configuration for easier network administration.
- Improved header structure with less processing overhead.
How do IPv4 and IPv6 work?
- The 128-bits in the IPv6 address are eight 16-bit hexadecimal blocks separated by colons. For example, 2dfc:0:0:0:0217:cbff:fe8c:0.
- IPv4 addresses are divided into "classes" with Class A networks for a few huge networks, Class C networks for thousands of small networks, and Class B networks that are in between. IPv6 uses subnetting to adjust network sizes with a given address space assignment.
- IPv4 uses class-type address space for multicast use (224.0.0.0/4). IPv6 uses an integrated address space for multicast, at FF00::/8.
- IPv4 uses "broadcast" addresses that force each device to stop and look at packets. IPv6 uses multicast groups.
- IPv4 uses 0.0.0.0 as an unspecified address, and class-type address (127.0.0.1) for loopback.
- IPv6 uses :: and ::1 as unspecified and loopback address respectively.
- IPv4 uses globally unique public addresses for traffic and "private" addresses. IPv6 uses globally unique unicast addresses and local addresses (FD00::/8).
HPE Juniper Networking Implementation
HPE Juniper Networking complies with RFC 5952 in the standard assignment and display rules for IPv6 addresses. These rules mean that devices must accept all methods of address entry.
Junos Address Aware is software for Juniper MX routers that helps conserve IPv4, ensure IPv4/IPv6 coexistence, and transition to IPv6.
FAQs
Why are people switching from IPv4 to IPv6?
The internet is rapidly growing, with an influx of new subscribers, Internet-enabled devices, and applications. Enhancements to IPv4 are needed to support this. IPv6 is built on the functionality of IPv4 and supports the continued global expansion of the Internet, creating a much larger pool of IP addresses and improving Internet addressing, configuration, maintenance, and security capabilities.
Can you use both IPv4 and IPv6?
Yes. A device that supports dual-stack IPv4/IPv6 addressing can interoperate equally with IPv4-only, IPv6-only, and other dual-stacked IPv4/IPv6 devices. When two communicating devices are both dual stacked, they agree on which IP version to use.
Which type of interface card supports Carrier-Grade Network Address Translation (CGNAT)?
The Junos OS enables its users to implement and scale their CGNAT solutions based on the type of service interfaces used for the implementation. The MS-MPC, MS-MIC, and MX-SPC3 interface cards for Juniper MX Series Universal Routing Platforms, for example, perform compute-intensive CGNAT services.