IPv6; Cloud Networking

IPv6

Why IPv6?

IPv4 uses 32-bit addresses = ~4.3 billion unique addresses
The internet has more than 4.3 billion devices — IPv4 addresses are exhausted
IPv6 uses 128-bit addresses = 340 undecillion (3.4 × 10^38) unique addresses

IPv6 Address Format

IPv4: 192.168.1.100  (32 bits, decimal notation)
IPv6: 2001:0db8:85a3:0000:0000:8a2e:0370:7334  (128 bits, hex notation)

Simplified: Remove leading zeros and consecutive groups of zeros:

2001:db8:85a3::8a2e:370:7334

IPv6 vs IPv4

Feature	IPv4	IPv6
Address size	32 bits	128 bits
Notation	Decimal dotted	Hexadecimal colon
Total addresses	~4.3 billion	~340 undecillion
Header size	20 bytes	40 bytes
NAT	Required	Not needed
Broadcast	Yes	No (multicast instead)
Auto-configuration	DHCP needed	SLAAC built-in
IPSec	Optional	Built-in
Fragmentation	At routers	Only at source

IPv6 Address Types

Type	Description	Example
Unicast	One-to-one communication	2001:db8::1
Multicast	One-to-many	ff02::1 (all nodes)
Anycast	Nearest of a set	Routing to nearest server
Link-Local	Used only on local link	fe80::/10
Global Unicast	Public internet addresses	2000::/3
Loopback	::1	Same as 127.0.0.1

Cloud Networking

What is Cloud Networking?

Cloud networking provides networking infrastructure and services through cloud providers (AWS, Azure, GCP).

Key Cloud Networking Concepts

Concept	Description
VPC (Virtual Private Cloud)	Isolated virtual network in the cloud
Subnets	Segments of VPC (public/private)
Internet Gateway	Connects VPC to the internet
NAT Gateway	Allows private subnets to access internet
Security Groups	Virtual firewall for instances
NACLs	Network ACLs — subnet-level firewall
Load Balancer	Distribute traffic across multiple instances
CDN	Content Delivery Network (CloudFront)
Route 53	AWS DNS service
VPN Gateway	Site-to-site VPN to on-premises
Direct Connect	Dedicated private connectivity
VPC Peering	Connect multiple VPCs

AWS Networking Architecture Example

Internet
    |
Internet Gateway
    |
VPC (10.0.0.0/16)
├── Public Subnet (10.0.1.0/24)
│   ├── Load Balancer
│   └── NAT Gateway
└── Private Subnet (10.0.2.0/24)
    ├── EC2 (web server)
    └── RDS (database)

IPv6 Addressing and Operation

An IPv6 address contains 128 bits and is written as eight hexadecimal groups. Leading zeroes may be omitted. One continuous run of zero groups may be replaced by :: once. The prefix length states how many high-order bits identify the network. A /64 prefix is the normal IPv6 LAN size.

Global unicast addresses are Internet routable. Link-local addresses begin with fe80::/10 and operate only on the local link. Unique local addresses use fc00::/7 for private organizational communication. Multicast sends to a group. IPv6 has no broadcast address. Anycast assigns the same address to several interfaces and routing selects a nearby instance.

Neighbor Discovery uses ICMPv6 in place of ARP. Router advertisements announce prefixes and default-router information. Stateless address autoconfiguration combines an advertised prefix with an interface identifier. DHCPv6 may supply addresses or other configuration. Duplicate Address Detection checks a new address before normal use. Routers do not fragment IPv6 packets; the source uses Path MTU Discovery and fragments when necessary.

Cloud Virtual Networking

A cloud virtual network is an isolated address space divided into subnets. Route tables decide where packets go. An Internet gateway provides public routing. A NAT gateway allows private IPv4 instances to initiate Internet connections. Security groups commonly provide stateful interface filtering while network access control lists may apply stateless subnet rules.

Load balancers distribute traffic across healthy targets. Private endpoints keep service traffic inside the provider network. Peering joins selected virtual networks while transit hubs connect many networks through central routing. Hybrid networks use VPN tunnels or dedicated circuits. Correct design requires non-overlapping address ranges, explicit routes, narrow security rules and DNS that resolves the intended private or public address.