Linux:Network

• https://en.wikipedia.org/wiki/List_of_TCP_and_UDP_port_numbers

Checks

Common

# List route table
route -n

# Display network connections and current states
netstat

# Check listening ports, connected remote IPs, processes, states and more
netstat -taupen

# Check listening ports and IPs of the local server
netstat -tulpn

# List the routing table
netstat -r

# List verbose common TCP and ICMP information
netstat -s

# Show all active network connections
nmcli connection show

# Show active and unactive network connections
nmcli dev status

# List iptable rules (Nftables)
iptables -nvL

# List iptable rules (Legacy iptables)
iptables-legacy -nvL

# Test specific IP and port combination for connectivity
telnet 172.16.2.1 22

# Wireshark on a specific interface to a file, listening on a local port and for a remote IP
tshark -p -i bond0 -w file.pcap -f "port 443 and host 172.16.16.25"

# List available routers
ip netns

DNS

• https://intodns.com/

# Lookup reverse DNS host information
dig -x 10.0.2.15

# Lookup reverse DNS host information
host 10.0.2.15

# Lookup DNS host information
nslookup 10.0.2.15

Network

RHEL

Generic Interface

# /etc/sysconfig/network-scripts/ifcfg-ens128
BOOTPROTO=static
HWADDR=ab:cd:ef:gh:ij:kl
IPADDR=192.168.10.2
NETMASK=255.255.255.0
NAME=ens128
STARTMODE=auto
UUID=0a8d3485-d512-46da-8225-19f4721813c1
GATEWAY=192.168.10.1
DEVICE=ens128

Generic VLAN Interface

# /etc/sysconfig/network-scripts/ifcfg-eno2.100
VLAN=yes
TYPE=Vlan
PHYSDEV=eno2
VLAN_ID=100
NAME=eno2.100
BOOTPROTO=static
HWADDR=ab:cd:ef:gh:ij:kl
IPADDR=192.168.100.217
NETMASK=255.255.255.0
STARTMODE=auto
UUID=689cff6f-c750-4db7-936c-234fb80b6018
GATEWAY=192.168.100.1

VLAN Bond interface configuration

Virtual Bond Master

BONDING_OPTS="mode=802.3ad miimon=100"
TYPE=Bond
BONDING_MASTER=yes
PROXY_METHOD=none
BROWSER_ONLY=no
IPV6INIT=no
NAME=bond0
UUID=7bb91614-6ffe-4bdc-9b37-c6e9d37f6987
DEVICE=bond0
ONBOOT=yes
AUTOCONNECT_PRIORITY=9
AUTOCONNECT_RETRIES=0
AUTOCONNECT_SLAVES=yes
MTU=1500

Physical bond Slaves

# /etc/sysconfig/network-scripts/ifcfg-ens1
TYPE=Ethernet
NAME=ens1
UUID=c6a4da43-b84a-44f4-b49f-4bdc717d4238
DEVICE=ens1
ONBOOT=yes
AUTOCONNECT_PRIORITY=9
AUTOCONNECT_RETRIES=0
MASTER_UUID=7bb91614-6ffe-4bdc-9b37-c6e9d37f6987
MASTER=bond0
SLAVE=yes

# /etc/sysconfig/network-scripts/ifcfg-ens2
TYPE=Ethernet
NAME=ens2
UUID=ca09a126-a082-4620-a920-be45269e5d8a
DEVICE=ens2
ONBOOT=yes
AUTOCONNECT_PRIORITY=9
AUTOCONNECT_RETRIES=0
MASTER_UUID=7bb91614-6ffe-4bdc-9b37-c6e9d37f6987
MASTER=bond0
SLAVE=yes

VLAN 100 Interface

# /etc/sysconfig/network-scripts/ifcfg-vlan-bond0.100
VLAN=yes
TYPE=Vlan
PHYSDEV=bond0
VLAN_ID=100
REORDER_HDR=yes
GVRP=no
MVRP=no
HWADDR=
PROXY_METHOD=none
BROWSER_ONLY=no
BOOTPROTO=none
IPADDR=192.168.100.10
PREFIX=24
DEFROUTE=yes
IPV4_FAILURE_FATAL=no
NAME=vlan-bond0.100
UUID=83b0e31c-9a9f-47da-9dc6-645796bc47aa
ONBOOT=yes
AUTOCONNECT_PRIORITY=9
AUTOCONNECT_RETRIES=0
GATEWAY=192.168.100.1

Ubuntu/Debian

Netplan

# Apply the configuration, but if the dialogue is left unconfirmed, the configuration will be reverted.
netplan try

# Apply the configuration
netplan apply

Generic interface

# /etc/netplan/60-cloud-init.yaml
network:
    version: 2
    ethernets:
        ens7:
           addresses:
              - 192.168.0.23/24
           match:
               macaddress: ab:cd:ef:gh:ij:kl
           mtu: 1500
           set-name: ens7
           nameservers:
               addresses: [1.1.1.1.1, 8.8.8.8]
           routes:
              - to: default
                via: 192.168.0.1

VLAN Interface

# /etc/netplan/01-eno1-interface.yaml
network:
    version: 2
    ethernets:
        eno1: {}
    vlans:
        eno1.10:
            id: 10
            link: eno1
            addresses: [192.168.1.1/24]
        eno1.20:
            id: 20
            link: eno1
            addresses: [192.168.2.1/24]
            nameservers:
              addresses:
                - 1.1.1.1
                - 8.8.8.8
              search: []
            routes:
              - to: default
                via: 192.168.0.1
        eno1.30:
            id: 30
            link: eno1
            addresses: [192.168.3.1/24]

Empty Interface

# /etc/netplan/02-eno2-interface.yaml
network:
  version: 2
  ethernets:
    eno2:
      dhcp4: false
      dhcp6: false

Networkmanager

Generic interface

# /etc/network/interfaces.d/ens160.conf
auto ens160
iface ens160 inet static
    address 192.168.23.7
    netmask 255.255.255.0
    gateway 192.168.23.1