VLSM: one block, subnets cut to size

The idea

Cut one block into subnets of different sizes, so nothing is wasted. branchRouter, a router, turns a branch office's 10.0.4.0/24 into a staff LAN, a guest LAN, a printer LAN and a link to coreRouter at headquarters.

Steps

1. One block, cut to size

   Equal pieces waste addresses, so each network gets a prefix that fits its devices: that is VLSM. branchRouter has a card in each, all cut from 10.0.4.0/24, biggest first, each starting on a multiple of its own size, so the pieces never overlap.

   branchRouter:~# ip -4 -br addr show

2. Where one subnet ends

   Subnets carved from one block touch but never overlap, so one address further can mean another network. Ask branchRouter about 10.0.4.63, the end of the staff LAN, then 10.0.4.64, one address further.

   branchRouter:~# ip route get 10.0.4.63
   branchRouter:~# ip route get 10.0.4.64