IPv4 has 4.3 billion addresses; IPv6 has 3.4 x 10^38. The book covers subnetting, NAT, CIDR, and the operational reality of dual-stack networks.
3.2 Network Addressing - IPv4 and IPv6
IPv4 vs IPv6
Property
IPv4
IPv6
Address size
32 bits
128 bits
Space
~4.3 billion
3.4 x 10^38
Notation
Four dotted decimals
Eight hex groups
NAT
Common
Not needed
Auto-config
DHCP
SLAAC + DHCPv6
Private ranges
10/8, 172.16/12, 192.168/16
ULA (fc00::/7)
CIDR notation - prefix to host count
Prefix
Usable hosts (approx)
Typical use
/30
2
Point-to-point links
/28
14
Small DMZ
/24
254
Office floor / small VLAN
/22
1,022
Branch
/16
65,534
Site
/8
16.7 million
Enterprise (private)
Worked example - planning a /28 for a branch
Address
Use
192.168.10.0
Network
192.168.10.1
Default gateway
192.168.10.2-14
13 usable hosts
192.168.10.15
Broadcast
Plenty for a small branch; insufficient if you add a guest VLAN.
Common pitfalls
Pitfall
Consequence
Allocating too small
Run out two years in
Overlapping private ranges
VPNs break between sites
IPv6 firewall left open
Hosts exposed globally
Mentor’s tip: IPv4 + NAT + CIDR is the legacy daily reality; IPv6 + SLAAC is the future. Dual-stack everything. Plan address space for 3-5 years of growth and document the renumber path before you need it.
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