Bridging: Build a Software Switch

This host is about to carry VMs, so it needs a software switch: a Linux bridge. Four dummy interfaces stand in for the VM ports, and the host's own address currently lives on one of them.

/root/case/assignment.env names the bridge to create, the ports that join it, one spare port that must stay out, and the host address (all differ per session; /root/case/brief.txt has the details). On the live system:

1. Create the bridge and bring it up.

2. Make exactly the assigned ports members of it. The spare must not be enslaved.

3. Move the host address (same address and prefix) from the port it's on to the bridge. Once that port is a bridge member, frames arriving on it belong to the bridge, so an address left on the port stops answering.

Grading reads the live links and addresses (ip -br link, ip -br addr, bridge link), so any construction and order passes. Nothing needs to survive a reboot.