# Networking

> Markdown source of <https://docs.calebsargeant.com/computing/linux/networking/>.

## IPTables

## Creating & Deleting Rules

**Create**

``` bash
iptables -A INPUT -i eth0 -p tcp --dport 80 -j ACCEPT
iptables -A INPUT -i eth0 -p tcp --dport 443 -j ACCEPT
```

**Delete**

``` bash
iptables -D INPUT -i eth0 -p tcp --dport 80 -j ACCEPT
iptables -D INPUT -i eth0 -p tcp --dport 443 -j ACCEPT
```

## List & Delete Rules

``` bash
# List the rules
iptables -L INPUT --line-numbers

# Delete rule 2 for example
iptables -D INPUT 2

# Specify a table
iptables -t nat -D PREROUTING 1
```

## LACP

``` bash
sudo apt-get update -y && sudo apt-get upgrade -y
sudo service networking stop
sudo nano /etc/network/interfaces

#/etc/network/interfaces
auto lo
iface lo inet loopback

iface eno1 inet manual
bond-master bond0

iface eno2 inet manual
bond-master bond0

auto bond0
iface bond0 inet manual
bond-mode 4
bond-miimon 100
bond-lacp rate 1
bond-slaves none

auto br0
iface br0 inet static
address 10.0.0.253
gateway 10.0.0.1
netmask 255.255.255.0
bridge-ports bond0
bridge-stp off
bridge-fd 0
bridge-maxwait 0
#

sudo service networking start
```

## Netcat

``` bash
# Check RADIUS UDP 1812 Port Status
nc -vnzu 10.11.12.13 1812
```

## Dig

A & CNAME: `dig @dnsserver.example.com +short domain.com` NS: `dig @dnsserver.example.com +short NS domain.com` MX: `dig @dnsserver.example.com +short MX domain.com` PTR: `dig @dnsserver.example.com +short -x 10.11.12.13`

### Public IP

Use `208.67.222.222` instead of resolver1 if no DNS. `dig +short myip.opendns.com @resolver1.opendns.com`

## Change Hostname

``` bash
sudo hostnamectl set-hostname <newhostname>
sudo nano /etc/hosts
```

## Netplan

Static vs dynamic IP Address configuration.

`sudo nano /etc/netplan`

``` yaml
# DYNAMIC (defaults)
network:
    version: 2
    ethernets:
        eth0:
            dhcp4: true
            match:
                macaddress: xx:xx:xx:xx:xx:xx
            set-name: eth0

# STATIC
network:
    ethernets:
        eth0:
            addresses:
            - 10.0.2.3/24
            gateway4: 10.0.2.1
            nameservers:
                addresses:
                - 10.0.2.1
                search:
                - example.com
    version: 2
```

## Ubuntu 16 - Change IP & Hostname

**Static IP**

``` bash
cd /etc/sysconfig/network-scripts/
vi ifcfg-eth0
  DEVICE=eth0
  BOOTPROTO=none
  ONBOOT=yes
  NETMASK=xxx.xxx.xxx.xxx
  IPADDR=xxx.xxx.xxx.xxx
  TYPE=Ethernet
vi /etc/sysconfig/network
  NETWORKING=yes
  NETWORKING_IPV6=no
  HOSTNAME=hostname.domainname.co.za
  GATEWAY=xxx.xxx.xxx.xxx

/etc/init.d/network restart
```

**Dynamic IP**

`dhclient ethx` or:

``` bash
cd /etc/sysconfig/network-scripts/
vi ifcfg-eth0
  DEVICE=eth0
  BOOTPROTO=dhcp
  ONBOOT=yes
  TYPE=Ethernet

vi /etc/sysconfig/network
  NETWORKING=yes
  NETWORKING_IPV6=no
  HOSTNAME=hostname.domainname.co.za
  GATEWAY=xxx.xxx.xxx.xxx

/etc/init.d/network restart
```

**Hostname Change**

``` bash
hostname --fqd
vi /etc/sysconfig/network
  HOSTNAME=<new_hostname>
vi /etc/hosts
  <ipaddr_of_server> <new_hostname.domain> <hostname>
reboot
```