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IPv4 vs IPv6 Cheat Sheet
Comprehensive comparison of IPv4 and IPv6 addressing
📍 IPv4
192.168.1.1
32-bit, 4.3 billion addresses
📍 IPv6
2001:db8::8a2e:370:7334
128-bit, 340 undecillion addresses
| Feature | IPv4 | IPv6 | IPv4 Example | IPv6 Example |
|---|---|---|---|---|
| Address Format | 32-bit, dotted decimal | 128-bit, hexadecimal colon | 192.168.1.1 | 2001:0db8:85a3::8a2e:0370:7334 |
| Address Space | ~4.3 billion addresses | ~340 undecillion addresses | Exhausted | Effectively unlimited |
| Header Size | 20-60 bytes (variable) | 40 bytes (fixed) | Options add overhead | Simplified, faster processing |
| Fragmentation | Routers and hosts | Sending host only | DF flag, MF flag | Path MTU Discovery required |
| Broadcast | Yes (255.255.255.255) | No (multicast instead) | Network broadcast | FF02::1 (all nodes) |
| Multicast | Optional, 224.0.0.0/4 | Built-in, required | Class D addresses | FF00::/8 |
| Anycast | Implemented in BGP | Native support | DNS root servers | Same address, nearest node |
| ARP | Address Resolution Protocol | NDP (Neighbor Discovery) | Broadcasts for MAC | ICMPv6 solicitation |
| DHCP | DHCP required for auto-config | SLAAC or DHCPv6 | Centralized assignment | Can self-configure |
| IPSec | Optional | Mandatory (spec), optional (practice) | Must be added | Built into protocol |
| NAT | Commonly used | Not needed (but NPTv6 exists) | Extends address space | End-to-end connectivity |
| Checksum | Header checksum | None (relies on L2/L4) | Calculated at each hop | Faster routing |
| Loopback | 127.0.0.1 | ::1 | localhost | localhost |
| Link-Local | 169.254.0.0/16 (APIPA) | fe80::/10 | Automatic when no DHCP | Always present on interface |
| Private Addresses | 10.x, 172.16-31.x, 192.168.x | fc00::/7 (ULA) | RFC 1918 | Unique Local Addresses |
| Global Unicast | All public IPs | 2000::/3 | Internet-routable | Internet-routable |
| Subnetting | Variable (/0 to /32) | /64 standard for LANs | CIDR notation | First 64 bits = network, last 64 = interface |
| Notation Shorthand | None | Leading zeros omit, :: for consecutive zeros | Full form required | 2001:db8::1 |
| Transition Tech | N/A | Dual-stack, tunneling, NAT64 | N/A | 6to4, Teredo, ISATAP |
| DNS Records | A record | AAAA record | Maps to IPv4 | Maps to IPv6 |
🎯 Exam Focus
- • IPv4: 32-bit, dotted decimal
- • IPv6: 128-bit, hexadecimal colons
- • IPv6 uses NDP instead of ARP
- • IPv6 can use SLAAC (auto-config)
- • IPv6 link-local: fe80::/10
- • IPv6 loopback: ::1