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L2.1 — Network Layer #2 continues the Internet Layer material, covering IPv6 address scopes, IPv4 vs IPv6 comparison and coexistence strategies (dual-stack, IPv6 Mostly), fragmentation differences, ICMP/ICMPv6, multicast, ARP and NDP (Neighbour Discovery Protocol), DHCP and DHCPv6/SLAAC address autoconfiguration (RFC4862, RFC7217, Privacy Extensions), DHCPv6-PD prefix delegation, subnets, netmasks/CIDR, and an introduction to routing.

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📋 At a Glance

• [ ] Know the three IPv6 address scopes: link-local (fe80::/10), global unicast (2000::/3), ULA (fc00::/7)
• [ ] Compare IPv4 vs IPv6 (header size, addressing, NAT, adoption, fragmentation)
• [ ] Explain dual-stack and "IPv6 Mostly" transition strategies
• [ ] Describe how fragmentation differs between IPv4 (any hop) and IPv6 (source only, Path MTU Discovery)
• [ ] Know what ICMP/ICMPv6 does and its role in diagnostics and IPv6 core functions
• [ ] Define multicast vs unicast vs broadcast and know key multicast addresses
• [ ] Explain ARP (IPv4) — broadcast "who has", unicast reply, arp cache
• [ ] Explain NDP (IPv6) — five ICMPv6 packet types, multicast-based, replaces ARP + ICMP Router Discovery
• [ ] Describe Router Advertisements — prefix, default router, flags for SLAAC/DHCPv6
• [ ] Explain SLAAC: prefix from RA + generated host part (RFC4862 EUI-64, RFC7217 pseudo-random, Privacy Extensions)
• [ ] Describe DHCP four-step process: DISCOVER → OFFER → REQUEST → ACK
• [ ] Describe DHCPv6: requires RAs, uses DUID, Solicit/Advertise/Request/Reply
• [ ] Explain DHCPv6-PD (prefix delegation) for distributing address blocks
• [ ] Know why we subnet (limit broadcast traffic, Ethernet max 1024 hosts recommended)
• [ ] Understand netmasks/prefix length — how many bits identify the network
• [ ] Know CIDR replaced classful addressing (Class A /8, Class B /16, Class C /24)
• [ ] Work through IPv4 and IPv6 netmask examples including non-byte boundaries (/25, /30)