network namespaces are kinda confusing

Illustration of an unhappy-looking stick figure with curly hair.

person: what does it MEAN for a process to have its own network??

namespaces usually have 2 interfaces

(+ sometimes more)

• the loopback interface (127.0.0.1/8, for connections inside the namespace)
• another interface (for connections from outside)

every server listens on a port and network interface(s)

0.0.0.0:8080 means “port 8080 on every network interface in my namespace”

127.0.0.1 stays inside your namespace

Illustration of a server, represented by a box with a smiley face, and a smiling stick figure with curly hair.

server, thinking: I’m listening on 127.0.0.1
person: that’s fine but nobody outside your network server namespace will be able to make requests to you!

your physical network card is in the host network namespace

Illustration of a rectangular box drawn with a dotted line. Inside it are:

• the label “host network namespace”
• 192.168.1.149, with an arrow pointing to it reading “requests from other computers”
• network card

other namespaces are connected to the host namespace with a bridge

Illustration of a rectangular box drawn with a dotted line. Inside it are:

• the label “host network namespace”
• three boxes, each labelled “container”