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Networking Advanced

What is Overlay Network?

A virtual network built on top of an existing physical network, enabling features like container networking and VPNs.

Overlay networks create logical network topologies independent of the underlying physical infrastructure. They encapsulate packets from the overlay network inside packets of the underlay network (tunneling). Technologies include VXLAN (extending Layer 2 across Layer 3 boundaries), WireGuard/IPsec (VPN tunnels), and container networking (Flannel, Calico, Weave). In Kubernetes, overlay networks enable pods on different physical hosts to communicate as if on the same LAN. Benefits include network isolation, simplified addressing, and infrastructure independence. The trade-off is encapsulation overhead reducing effective MTU and adding latency.

Related Terms

NAT (Network Address Translation)
A method of mapping private IP addresses to public IP addresses, allowing multiple devices to share a single public IP.
OSI Model
The seven-layer Open Systems Interconnection model that standardizes network communication functions from physical transmission to application protocols.
ICMP (Internet Control Message Protocol)
A network protocol used for diagnostic and error reporting, including ping and traceroute functionality.
VPN (Virtual Private Network)
A technology that creates an encrypted tunnel between your device and a remote server, securing internet traffic.
DHCP
A protocol that automatically assigns IP addresses and network configuration to devices on a network.
Token Bucket Algorithm
A rate limiting algorithm that allows burst traffic by accumulating tokens at a fixed rate and consuming them per request.
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