Networking

Ubuntu basics

To see network details:

ip a

Bring an interface up/down:

sudo ifconfig enp4s0 down
sudo ifconfig enp4s0 up

DNSMasq

I disabled systemd and use dnsmasq for bitpost routing.

It provides static IPs to LAN via MAC addresses.

It performs DNS caching. Use /etc/resolv.conf to set up fallback DNS.

Update to new ISP

I did this for google fiber on 2022/09/30.

Set up new ISP while keeping old
Update any ethernet cables and NIC cards; I need cat6 from google fiber router GRAY port (2Gbps); I ordered a 10G network card on Amazon, not here yet.
Remove old ISP cable from RJ45, plug in new ISP cable
ssh 192.168.22.1 to get a terminal to bitpost box
check that a new IP was obtained via `ip a`
RESTART THE FIREWALL, it MUST BE STARTED after the IP is obtained! This was the kicker that had me scratching my head for an hour.

sudo su -
edit_firewall
# Ctrl-D to save and exit and restart it

Check that you can ping google.com; check that LAN is up and ready
Go update ALL domains.google.com DNS records with the new IP!
Pray for IP stability! reddit commentors gave me hope, we will see...

Update to use new network card (NIC)

After ensuring that google fiber worked, I upgraded bitpost to a 10g NIC card. systemd added new interface names for the two RJ45 jacks on the card.

There are THREE PLACES where those names must be changed:

ubuntu/bitpost/root/stronger_firewall_and_save
ubuntu/bitpost/etc/dnsmasq.d/mdm_lan_dnsmasq.conf
ubuntu/bitpost/etc/netplan/00-installer-config.yaml

Go ahead and cable bitpost directly to the HDMI display, and get a terminal going there.
Power down, install the NIC, power up.
Type `ip a` to see the new network interface names.

# MDM moving from 1Gbps internal mobo nics (enp4/5) to 10Gbps Intel nic card (enp10s0f0/1)
#1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN group default qlen 1000
#2: enp5s0f1: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc fq_codel state UP group default qlen 1000
#3: enp4s0: <NO-CARRIER,BROADCAST,MULTICAST,UP> mtu 1500 qdisc mq state DOWN group default qlen 1000
#4: enp10s0f0: <BROADCAST,MULTICAST> mtu 1500 qdisc noop state DOWN group default qlen 1000
#5: enp10s0f1: <BROADCAST,MULTICAST> mtu 1500 qdisc noop state DOWN group default qlen 1000

Restart the network with the new plan, via `sudo netplan apply`, and verify with `ip a`.
Restart the firewall to use the newly available network names, via:

sudo su -
edit_firewall

Restart dnsmasq to use the new network name, via `sudo service dnsmasq restart`.
The IP changed due to a new NIC MAC, so once things settle down, go update all DNS records, and (again) restart dnsmasq to clear its cache.

WOW, I now have >1Gbps networking to bitpost.com, abettertrader.com, etc!

Force apt to use a proxy

Edit /etc/apt/apt.conf:

Acquire::http::Proxy "http://myproxy.com:####";