Networking

Part 3 kept everything on one machine: namespaces as workloads, veth as cables, bridge or macvlan or ipvlan as the attachment. That is enough for a single Docker host. Two hosts do not share a broadcast domain just because both run Linux. Something has to carry Ethernet (or IP) across the real network between them. VXLAN is one common way to do that. CNI is something else entirely: a contract so Kubernetes (and other runtimes) can plug a pod into whatever network architecture you chose. ...

Part 1 built Layer 2 stacks on a host. Part 2 moved packets between IP networks. Both assumed one network stack: one set of interfaces, routes, and firewall rules. This post isolates whole stacks on the same machine. A network namespace is a private view of networking. A veth pair is a cable between views. A bridge, macvlan, or ipvlan is how those cables join a shared domain or a parent NIC. ...

In VLANs, Bonding, and Bridging, the host stayed inside one or more Layer 2 domains: bonds for uplinks, VLANs for separation, bridges for VMs. That stack answers “who shares this Ethernet segment?” This post answers a different question: how does a Linux box move packets between IP networks? That is routing — forwarding, policy routing when you have more than one path, and nftables rules that decide what is allowed to cross. ...

Linux networking becomes much easier to reason about when you treat interfaces as layers. A physical NIC can become part of a bond. A VLAN interface can sit on top of that bond. A bridge can sit on top of the VLAN. The host’s IP address belongs on whichever layer represents the host on that network. This post focuses on three building blocks that often appear together on servers, virtualization hosts, routers, and lab machines: ...

Recently I had problem with my Ubuntu, Whenever I tried to open a website my Chromium told me that a Network Change has been detected and after 1-2 reload that sites would load and sometimes failed to load fully. After looking up for that problem, I found out many other people had same problem and it has something to do with “avahi-daemon”. Solution According to the links I found in Ubuntu forums, this problem comes from IPv6 in Ubuntu and disabling that service will fix it, I tried it and it worked: ...