update debian networking instructions

zk/Configuring_internet_connection_on_Debian.md

@@ -0,0 +1,77 @@
+---
+tags: [networks, internet, Debian, linux, Ethernet]
+---
+
+## Ethernet
+
+First identify the name of your Ethernet interface with
+[`ip addr show`](./View_IP_addresses.md). Example output:
+
+```
+ enp1s0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc fq_codel state UP group default qlen 1000
+    link/ether 40:b0:34:37:40:40 brd ff:ff:ff:ff:ff:ff
+    inet 192.168.178.53/24 brd 192.168.178.255 scope global enp1s0
+```
+
+That last line is configured via `/etc/network/interfaces`. If you have not set
+this up, the top line will say `DOWN` instead of `UP` and you will not have
+internet access over Ethernet.
+
+The follwing example of `/etc/network/interfaces` is a common default:
+
+```
+auto enp1s0
+iface enp1s0 inet static
+    address 192.168.178.49
+    netmask 255.255.255.0
+    gateway 192.168.178.1
+    dns-nameservers 8.8.8.8 8.8.4.4
+```
+
+Sets the following:
+
+- connect automatically as soon as Ethernet port activated
+- use the `enp1s0` interface and insist on static IP from [DHCP](./DHCP.md)
+- use the static IP address `192.168.178.49`
+- use standard subnet masking
+- use Google as the preferred and fallback DNS
+
+Restart networking:
+
+```sh
+sudo systemctl restart networking
+```
+
+Confirm connection again with `ip addr show` or
+`sudo systemctl status networking`.
+
+## Turn the Ethernet interface on/off
+
+```sh
+ifup enp1s0
+ifdown enp1s0
+```
+
+### Use dynamic local IP address
+
+If you don't want to use a static IP, the contents of `/etc/network/interfaces`
+is more minimal:
+
+```
+auto enp1s0
+iface enp1s0 inet dhcp
+```
+
+Basically you just let DHCP do the work of negotiating the IP address from the
+router.
+
+## Contrast with other Linux operating systems
+
+Arch uses `systemd-resolvd` and NetworkManager. You won't find
+`etc/network/interfaces`.
+
+To check network status on Arch use:
+
+```sh
+systemctl status NetworkManager
+```

zk/IP_addresses.md

@@ -1,6 +1,5 @@
 ---
 tags: [networks, internet]
-created: Friday, August 16, 2024
 ---
 
 ## IPv4 vs IPv6

zk/Network_scanning.md

@@ -1,6 +1,6 @@
 ---
 id: ippn
-tags: [networks, procedural, Linux]
+tags: [networks, procedural, Linux, dns]
 created: Monday, June 10, 2024
 ---
 

zk/View_IP_addresses.md

@@ -23,4 +23,4 @@ link/ether 90:2e:16:53:98:b9 brd ff:ff:ff:ff:ff:ffinet
 ```
 
 The most important line is the third. This indicates my IP address
-(`192.168.0.3/24`) including its subnet mask.
+(`192.168.0.3/24`) including its [subnet mask](./IP_addresses.md).