Network

A host that receives an ARP reply has no way to check whether the reply is real. Broadcast “what is the MAC of gateway 192.168.1.1?” and whoever answers, that answer gets written straight into the cache. No authentication, no integrity check. ARP even accepts a reply nobody asked for (a Gratuitous ARP) and overwrites the existing cache entry with it. An attacker puts a fake reply into that gap. Tell the victim “the gateway’s MAC is mine” and the gateway “the victim’s MAC is mine” at the same time, and all traffic between the two routes through the attacker. It is a textbook man-in-the-middle (MITM) attack, reproduced below in an isolated lab. ...

Overview In the previous post, we installed the Traefik ingress controller and configured secure access to management interfaces by separating internal and external services. This post covers how to configure DDNS and port forwarding to enable external internet access to services running in the homelab Kubernetes cluster. Network Architecture Summary First, let’s briefly summarize the network architecture configured in the previous post: Internal Load Balancer (192.168.0.200): Exposes only management interfaces like ArgoCD, Longhorn, and Traefik dashboard, accessible only from within the internal network. External Load Balancer (192.168.0.201): Exposes only public services like blogs and personal projects, accessible from the external internet through router port forwarding. ...

Overview In the previous post, we installed the Longhorn distributed storage system to build a persistent storage environment where data is retained even when pods restart or move to different nodes. This post covers installing the Traefik ingress controller on a homelab Kubernetes cluster and configuring secure access to management interfaces from the internal network. Choosing an Ingress Controller There are several methods for exposing Kubernetes services externally in a homelab environment: ...

In IPv4, a host needed several different protocols just to start talking. ARP found MAC addresses, ICMP Router Discovery advertised the gateway, DHCP handed out addresses, and ICMP Redirect fixed routes, each running independently. IPv6 folds these four jobs into five message types over ICMPv6, and that consolidation mechanism is NDP (Neighbor Discovery Protocol). Following what each of those five messages looks like, and the order they fly in when a host joins a network, shows how NDP works. ...

What is ARP ARP (Address Resolution Protocol) is a network protocol defined in RFC 826 by the IETF in 1982. In TCP/IP networks, it dynamically discovers the MAC address (physical address) associated with a given IP address. It sits at the boundary between Layer 2 (Data Link Layer) and Layer 3 (Network Layer) of the OSI 7-layer model and maps logical addresses (IP) to physical addresses (MAC). In network communication, actual data transmission between devices relies on MAC addresses. The upper layer (Network Layer) works with IP addresses, but the lower layer (Data Link Layer) needs the destination’s MAC address to send packets. ARP performs this IP-to-MAC conversion. It broadcasts a query across the network, and only the device that owns the target IP responds. Because of this, ARP is an essential protocol in most local network environments, including Ethernet networks. ...

Split 192.168.1.0/24 into four pieces and they start at .0, .64, .128, and .192. None can start at 50. Memorizing the subnetting table, where /26 means 64 and /27 means 32, makes the numbers feel familiar, but a nonstandard boundary or a VLSM split breaks that memory. A CIDR prefix marks where the network bits end, and every boundary calculation reduces to a bit operation at that mark. The sections below walk through that bit operation and check each result with real output from Python’s ipaddress. ...

A static IP address is an IP address manually specified by a network administrator instead of being dynamically assigned from a DHCP server. It is essential in environments where the IP address must not change, such as server operation, remote access, and network service hosting. Ubuntu 24.04 LTS uses Netplan as the default network configuration tool and also supports nmcli and nmtui interfaces through NetworkManager, allowing users to configure networks in their preferred way. ...