L3 — Network

IP packets, routing between subnets, the scope of most dynamic routing protocols.

What lives at L3

• IPv4 / IPv6
• ICMP
• OSPF, BGP, EIGRP, IS-IS
• IPsec (encapsulation)
• GRE, VXLAN (tunnels crossing L3)
• NAT / PAT

Cloud equivalents

• AWS VPC route tables
• Azure VNet routes + UDRs