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Networking Fundamentals · Foundational

Dual Stack

Running IPv4 and IPv6 simultaneously on the same devices and network.

Definition

Dual stack is the most common and recommended IPv6 transition method: hosts and routers have both address families and choose based on DNS results, usually preferring IPv6 (with Happy Eyeballs fallback). It requires maintaining two routing and security policies. Over time, IPv6-only with NAT64 is replacing dual stack in some networks.

Example

A laptop with both 192.168.1.20 and 2001:db8:1::20 is dual-stacked.

Exam tip

When asked for the preferred transition method that runs both protocols natively, choose dual stack.

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