Network is UP

So every time I swap the connectors the network thinks I'm swapping NICs. 

Needless to say, the ones here are backwards ;)
So now I'm going to use mac address

camelot

tux@localhost:~$ sudo ip addr flush dev enp3s0f4u1
sudo ip addr add 10.20.30.1/24 dev enp3s0f4u1
sudo ip link set enp3s0f4u1 up
[sudo] password for tux: 
tux@localhost:~$ ping -c 3 10.20.30.2
PING 10.20.30.2 (10.20.30.2) 56(84) bytes of data.
64 bytes from 10.20.30.2: icmp_seq=1 ttl=64 time=2.66 ms
64 bytes from 10.20.30.2: icmp_seq=2 ttl=64 time=1.64 ms
64 bytes from 10.20.30.2: icmp_seq=3 ttl=64 time=1.35 ms

--- 10.20.30.2 ping statistics ---
3 packets transmitted, 3 received, 0% packet loss, time 2004ms
rtt min/avg/max/mdev = 1.352/1.885/2.661/0.561 ms
tux@localhost:~$ sudo nmcli con add type ethernet ifname enp3s0f4u1 con-name camelot-static \
    ipv4.method manual ipv4.addresses "10.20.30.1/24" ipv4.gateway "" ipv4.dns ""
Connection 'camelot-static' (370362b6-8c83-4889-a187-d692a5a39ace) successfully added.
tux@localhost:~$ sudo nmcli con mod camelot-static connection.autoconnect yes
tux@localhost:~$ 

updated

tux@localhost:~$ sudo nmcli con add type ethernet con-name camelot-static \
    ipv4.method manual ipv4.addresses "10.20.30.1/24" \
    802-3-ethernet.mac-address "A0:CE:C8:56:E2:4C" \
    connection.autoconnect yes
Connection 'camelot-static' (1281ac5f-da9b-450f-882b-923566b5ce9c) successfully added.
tux@localhost:~$ sudo nmcli con up camelot-static
Connection successfully activated (D-Bus active path: /org/freedesktop/NetworkManager/ActiveConnection/176)
tux@localhost:~$ ip addr show

 

tux

 allison@frodo:~$ ip link
1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN mode DEFAULT group default qlen 1000
    link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
2: wlp3s0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc noqueue state UP mode DORMANT group default qlen 1000
    link/ether 9e:f1:18:ab:92:36 brd ff:ff:ff:ff:ff:ff permaddr 84:3a:4b:d3:95:50
16: enp0s20u2u1: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc fq_codel state UP mode DEFAULT group default qlen 1000
    link/ether a0:ce:c8:56:e2:4c brd ff:ff:ff:ff:ff:ff

allison@frodo:~$ sudo ip addr flush dev enp0s20u2u1
sudo ip addr add 10.20.30.2/24 dev enp0s20u2u1
sudo ip link set enp0s20u2u1 up

allison@frodo:~$ sudo nmcli con add type ethernet ifname enp0s20u2u1 con-name frodo-static \
    ipv4.method manual ipv4.addresses "10.20.30.2/24" ipv4.gateway "" ipv4.dns ""
[sudo] password for allison: 
Connection 'frodo-static' (d79bb57b-d3f2-468a-8b23-ba0673f1d306) successfully added.

allison@frodo:~$ sudo nmcli con mod frodo-static connection.autoconnect yes

allison@frodo:~$ sudo nmcli con down "Wired connection 1" 2>/dev/null
sudo nmcli con delete "Wired connection 1" 2>/dev/null

allison@frodo:~$ sudo nmcli con up frodo-static
Connection successfully activated (D-Bus active path: /org/freedesktop/NetworkManager/ActiveConnection/204)

---

🏡 Home Network 10.20.30

A simple, stable, no-DHCP, no-surprises wired LAN that connects my personal machines directly:

Hostname	IP Address	Interface	Role
Camelot	10.20.30.1	enp3s0f4u1	Anchor / Server
Frodo	10.20.30.2	enp0s20u2u1	Client / Peer
JohnnyCamelot	10.20.30.3	(future)	Optional
WindowsBox	10.20.30.x	(future)	Optional

This mini-LAN is used for direct Linux-to-Linux communication without DHCP, without router involvement, and without NetworkManager auto-assigning unwanted subnets like 10.42.x.x.

The goal:
Two machines that always come back with the same IPs, every reboot, every cable-move, every day.

---

🏰 1. Purpose of the Network

This network provides:

• A small, private wired LAN independent of Wi-Fi
• Stable static IPv4 addressing
• Predictable connectivity between machines
• Zero interference from DHCP, USB-tethering, or sharing modes
• A clean foundation for development, file transfer, testing, or just “making the machines talk”
• A sanity-preserving antidote to automatic volatile network profiles

This is “The Camelot Bridge.”

---

🔌 2. Physical Layout

Machines are directly connected with:

• USB-to-Ethernet adapters
• Standard Ethernet cable
• (Or via a passive switch — optional)

No router is required.
No gateway is used.
This is a flat Layer-2 link.

---

🗺️ 3. Subnet Details

Network:    10.20.30.0/24
Camelot:    10.20.30.1
Frodo:      10.20.30.2
Broadcast:  10.20.30.255
Gateway:    None (not used)
DNS:        None (not needed)

This is a standalone LAN segment.

---

🧱 4. Permanent Static Config (NetworkManager)

Camelot (10.20.30.1)

Interface: enp3s0f4u1

sudo nmcli con add type ethernet ifname enp3s0f4u1 con-name camelot-static \
    ipv4.method manual ipv4.addresses "10.20.30.1/24"

sudo nmcli con mod camelot-static connection.autoconnect yes

sudo nmcli con down "Wired connection 1" 2>/dev/null
sudo nmcli con delete "Wired connection 1" 2>/dev/null

sudo nmcli con up camelot-static

Frodo (10.20.30.2)

Interface: enp0s20u2u1

sudo nmcli con add type ethernet ifname enp0s20u2u1 con-name frodo-static \
    ipv4.method manual ipv4.addresses "10.20.30.2/24"

sudo nmcli con mod frodo-static connection.autoconnect yes

sudo nmcli con down "Wired connection 1" 2>/dev/null
sudo nmcli con delete "Wired connection 1" 2>/dev/null

sudo nmcli con up frodo-static

Once these are set, the IP assignments survive:

• Reboots
• Cable unplug/replug
• NetworkManager resets
• Device renaming
• 10.42.x.x “shared connection” pitfalls

---

🧪 5. Connectivity Test

Run from either machine:

ping 10.20.30.1
ping 10.20.30.2

You should always see:

0% packet loss

If not, check:

ip addr
ip link
ip neigh

---

✨ 6. The Camelot Bridge Rules

1. Use static IPs only.
2. Never leave NetworkManager in shared or auto-tether mode.
3. Bind IPs to the correct Ethernet NIC (Frodo: enp0s20u2u1, Camelot: enp3s0f4u1).
4. Leave Wi-Fi (wlp3s0) untouched.
5. Never mix Wi-Fi and this LAN — they’re separate networks.

6. If something breaks, run:

   ip addr show
   ip neigh show
   

   These two always reveal which interface is in use.

7. The subnet does not route to the internet — and it shouldn’t.

---

🧭 7. Future Nodes

You can safely add:

• JohnnyCamelot = 10.20.30.3
• WindowsBox = 10.20.30.100 (example)

Once you’re ready to deal with Windows, we’ll do:

• Static IP
• Disable automatic metric
• Disable random MAC
• Ensure proper Ethernet interface
• Add route appropriately

But not on a Sunday.

---

🗃️ 8. Backup of Profiles

To backup current profiles:

nmcli con show camelot-static > camelot-static.nmcli
nmcli con show frodo-static > frodo-static.nmcli

To restore:

nmcli con load camelot-static.nmcli
nmcli con load frodo-static.nmcli

---

🏁 9. Goal Achieved

This project gives me a:

• predictable,
• stable,
• frustration-free,
• two-machine wired LAN

that Just Works™ every time.

---

If you want, I can also:

✔ create a matching network-map.png diagram
✔ generate a setup script (setup-camelot-bridge.sh)
✔ add Windows instructions
✔ add troubleshooting section
✔ turn this into a tiny GitHub repo

Just say “Add it”.