Public ip address

As explained in Acing the CCNA Exam: Volume 2 Advanced Networking and Security

A public IPv4 address is an IPv4 address that is globally unique and intended for communication across the public internet.

A public IPv4 address is an IPv4 address that is not in an RFC 1918 range or another reserved range. It must be globally unique so internet routers can identify the intended destination. section 9.1 section 9.4

Distinguish public addressing from private addressing:

• RFC 1918 private ranges are 10.0.0.0/8, 172.16.0.0/12, and 192.168.0.0/16; private addresses may be reused in separate, disconnected networks. section 9.1 section 9.4
• Private IPv4 packets are not routable across the internet and are discarded by the ISP when sourced from or destined for private addresses. section 9.1
• NAT translates private addresses into public addresses so internally addressed hosts can communicate over the internet. section 9.0 section 9.2

Outbound NAT exchange

PC1 sends a packet to 8.8.8.8 using its private source address. R1 translates that source to a public IPv4 address before forwarding the packet; on the reply, R1 translates the destination back to PC1's private address. section 9.2.1

Figure 9.1 Public and private IPv4 addresses. Private IPv4 addresses can be freely used for internal networks and do not have to be globally unique. Public IPv4 addresses, used for communication over the internet, must be globally unique.

Compare globally unique public addresses with reusable private addresses across connected LANs. section 9.1

How Acing the CCNA Exam: Volume 2 Advanced Networking and Security covers it

How deep it goes

Defines uniqueness, routability, reserved-range exclusions, and NAT translation, but does not detail public-address allocation.

Examples

Uses overlapping private LAN subnets, documentation address ranges, 8.8.8.8, and a router-mediated NAT exchange.

What you can do after

Evaluate whether an IPv4 address is public and understand why NAT is required for private hosts using the internet.

How it connects

Connects public IPv4 addressing to private IPv4 addressing, Network Address Translation, IPv6, and CIDR.

liveBookmanning.com

Read Acing the CCNA Exam: Volume 2 Advanced Networking and Security on liveBook Get the book at manning.com

Also explained in

• 

  liveBookmanning.com
  Amazon Web Services in Action, Third Edition: An in-depth guide to AWSA public IPv4 address is an IPv4 network address routable from the public internet and assigned to an internet-facing resource.

Compare how 2 books explain public ip address →

Related concepts

• IPv4kind of · IPv4 is the fourth version of the Internet Protocol, using 32-bit addresses to identify network interfaces and packet sources or destinations.
• private ipv4 addresscontrasts with · A private IPv4 address is an address from a designated range intended for communication within private networks rather than direct routing on the public Internet.
• global unicast addressequivalent to · A global unicast address is an IPv6 unicast address that is globally unique and routable over the internet.
• Azure Load Balancerused by · Azure Load Balancer is a managed Azure service that distributes network traffic across backend resources according to configured rules and health status.
• network address translationproduced by · Network address translation is a networking technique that rewrites IP addresses and often transport-layer ports as traffic crosses a gateway or network boundary.

This explainer was generated by Manning's knowledge graph from the text of Acing the CCNA Exam: Volume 2 Advanced Networking and Security. The section links point to the parts of the book it draws on.