• ip a to see interfaces + ip addresses.
• ifw disable disables the ubuntu firewall.

To change the network configuration in new Ubuntu versions.

There is an .yml software in /etc/netplan. To apply changes use the next command:

netplan apply

network:
  version: 2
  renderer: networkd
  ethernets:
    enp3s0:
      addresses:
        - 10.10.10.2/24
      gateway4: 10.10.10.1
      nameservers:
          search: [mydomain, otherdomain]
          addresses: [10.10.10.1, 1.1.1.1]

network:
  version: 2
  renderer: networkd
  ethernets:
    enp3s0:
      dhcp4: true

network:
  version: 2
  renderer: NetworkManager

alfred@Y50-70:~$ nslookup couch00.dev.getfinancing.us
Server:		127.0.0.53
Address:	127.0.0.53#53

Non-authoritative answer:
Name:	couch00.dev.getfinancing.us
Address: 10.1.50.195
Name:	couch00.dev.getfinancing.us
Address: 10.1.51.200
Name:	couch00.dev.getfinancing.us
Address: 10.1.52.100

alfred@Y50-70:~$ route -n
Kernel IP routing table
Destination     Gateway         Genmask         Flags Metric Ref    Use Iface
0.0.0.0         192.168.1.1     0.0.0.0         UG    100    0        0 enp9s0
10.1.0.0        0.0.0.0         255.255.0.0     U     50     0        0 tun0
34.231.231.68   192.168.1.1     255.255.255.255 UGH   100    0        0 enp9s0
169.254.0.0     0.0.0.0         255.255.0.0     U     1000   0        0 virbr0
192.168.1.0     0.0.0.0         255.255.255.0   U     100    0        0 enp9s0
192.168.1.1     0.0.0.0         255.255.255.255 UH    100    0        0 enp9s0
192.168.122.0   0.0.0.0         255.255.255.0   U     0      0        0 virbr0
192.168.255.1   192.168.255.21  255.255.255.255 UGH   50     0        0 tun0
192.168.255.21  0.0.0.0         255.255.255.255 UH    50     0        0 tun0

You can query dns records with the dig command. To do that, for example, for obtaining the CNAME record for url6816.alfredgg.dev:

dig cname url6816.alfredgg.dev

• ipsec status tells you who is connected.
• ipsec reload reloads the config.
• ipsec restart restarts the service.

Locally and simply:

nmap localhost

Remotely:

nmap -Pn -p 51414 95.169.230.182

Comprueba el puerto 51414 de 95.169.230.182.

Hay la posibilidad de lanzarlo via web desde: http://nmap.online-domain-tools.com/

nmap -sP 192.168.1.*

nmap -sn 192.168.1.0/24

• https://medium.com/@docler/network-issues-simulation-how-to-test-against-bad-network-conditions-b28f651d8a96
• https://wiki.linuxfoundation.org/networking/netem

You will use “tc” command:

sudo tc qdisc add dev eth0 root netem delay 1s
sudo tc qdisc del dev eth0 root

For example, to simulate problems with dockers you will do the next:

1. docker inspect container → And take the value for the IPAddress
2. route -n → To see which device is used for that container
3. sudo tc qdisc add dev <device> root netem delay 1s
4. Test it with a ping.
5. sudo tc qdisc del dev <device> root

tc qdisc add dev eth0 root netem loss 5%
tc qdisc change dev eth0 root netem corrupt 2%
tc qdisc change dev eth0 root netem duplicate 1%

Previously you only need to edit the /etc/resolv.conf

In new versions Netplan manages the network. You can configure it on files places on /etc/netplan; these have an yml format.

This is an example:

network:
  version: 2
  renderer: networkd
  ethernets:
    ens3:
      dhcp4: no
      addresses:
        - 192.168.121.199/24
      gateway4: 192.168.121.1
      nameservers:
          addresses: [8.8.8.8, 8.8.4.4]

To update from changes do:

netplan apply

To list dns entries:

systemd-resolve --status

$ route -n
0.0.0.0         91.126.134.177  0.0.0.0         UG    100    0        0 ens18