Linux:Network: Difference between revisions

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# List verbose common TCP and ICMP information
# List verbose common TCP and ICMP information
netstat -s
netstat -s
# Show all active network connections
nmcli connection show
# Show active and unactive network connections
nmcli dev status


# List iptable rules (Nftables)
# List iptable rules (Nftables)
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</syntaxhighlight>
</syntaxhighlight>


=== DNS ===
== Network ==
* https://intodns.com/
=== NetworkManager ===
'''nmtui''' is a GUI-tool for managing NetworkManager connections.


<syntaxhighlight lang="bash">
==== Checks ====
# Lookup reverse DNS host information
<syntaxhighlight lang='bash'>
dig -x 10.0.2.15
# Show all active network connections
nmcli connection show


# Lookup reverse DNS host information
# Show connection information for interface ens5
host 10.0.2.15
nmcli connection show ens5


# Lookup DNS host information
# Show active and unactive network connections
nslookup 10.0.2.15
nmcli dev status
</syntaxhighlight>
 
==== nmcli ====
<syntaxhighlight lang='bash'>
# Bring logical interface ens6 up
nmcli device up ens6
 
# Turn off DHCP
nmcli con mod ens6 ipv4.method manual
nmcli con mod ens6 connection.autoconnect yes


# Lookup host information for google.com while using DNS-server 8.8.8.8
# Add an IP-address to interface ens6
nslookup google.com 8.8.8.8
nmcli connection modify ens6 ipv4.address "192.168.0.10/24"
 
# Add DNS-servers to interface ens6
nmcli connection modify ens6 ipv4.dns "8.8.8.8,1.1.1.1,196.168.0.1"
 
# Add a gateway to interface ens6
nmcli con mod ens6 ipv4.gateway "192.168.0.1"
 
# Add a default route to interface ens160
nmcli connection modify ens160 +ipv4.routes "0.0.0.0/0 192.168.3.100"
 
# Remove an IP-address from interface ens6
nmcli con mod ens6 -ipv4.addresses 192.168.0.11/24
 
# Apply changes to interface ens
nmcli device reapply ens6
</syntaxhighlight>
</syntaxhighlight>


== Network ==
=== RHEL ===
=== RHEL ===
==== Generic Interface ====
==== Generic Interface ====
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Generic DHCP Interfaces, but while ignoring the routes for an Interface and disabling DHCP on the other.
Generic DHCP Interfaces, but while ignoring the routes for an Interface and disabling DHCP on the other.
<syntaxhighlight lang='bash'>
<syntaxhighlight lang='yaml'>
network:
network:
     version: 2
     version: 2
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===== Generic static interface =====
===== Generic static interface =====
<syntaxhighlight lang='bash'>
You may have to disable automatic network-configuration:
# /etc/netplan/60-cloud-init.yaml
<syntaxhighlight lang='yaml'>
sudo bash -c 'echo "network: {config: disabled}" > /etc/cloud/cloud.cfg.d/99-disable-network-config.cfg'
</syntaxhighlight>
 
<syntaxhighlight lang='yaml'>
network:
network:
     version: 2
     version: 2
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           set-name: ens7
           set-name: ens7
           nameservers:
           nameservers:
               addresses: [1.1.1.1.1, 8.8.8.8]
               addresses: [1.1.1.1, 8.8.8.8]
           routes:
           routes:
               - to: default
               - to: default
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===== VLAN Interface =====
===== VLAN Interface =====
<syntaxhighlight lang='bash'>
<syntaxhighlight lang='yaml'>
# /etc/netplan/01-eno1-interface.yaml
network:
network:
     version: 2
     version: 2
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===== Empty Interface =====
===== Empty Interface =====
<syntaxhighlight lang='bash'>
<syntaxhighlight lang='yaml'>
# /etc/netplan/02-eno2-interface.yaml
network:
network:
   version: 2
   version: 2
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</syntaxhighlight>
</syntaxhighlight>


==== Networkmanager ====
==== Interface files ====
Classic <code>/etc/network/interfaces.d</code> files i.e. <code> /etc/network/interfaces.d/ens200.conf </code>
Otherwise use <code>/etc/network/interfaces </code>


===== Generic IPv4 =====
===== Generic IPv4 =====
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     netmask 255.255.255.0
     netmask 255.255.255.0
     gateway 192.168.23.1
     gateway 192.168.23.1
</syntaxhighlight>
===== Generic IPv6 =====
<syntaxhighlight lang='bash'>
# /etc/network/interfaces.d/ens3.conf
iface ens3 inet6 static
    address abcd:defg:0:1234:5123:abcd:abcd:1234
    netmask 48
    gateway abcd:defg::1
</syntaxhighlight>
</syntaxhighlight>


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         bond-mode 802.3ad
         bond-mode 802.3ad
         bond-xmit-hash-policy layer2+3
         bond-xmit-hash-policy layer2+3
</syntaxhighlight>
===== Generic IPv6 =====
<syntaxhighlight lang='bash'>
# /etc/network/interfaces.d/ens3.conf
iface ens3 inet6 static
address abcd:defg:0:1234:5123:abcd:abcd:1234
netmask 48
gateway abcd:defg::1
</syntaxhighlight>
</syntaxhighlight>

Latest revision as of 13:55, 25 September 2025


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

# 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

# Show interfaces with an IPv4 address
ip -4 a

# Show interfaces with an IPv6 address
ip -6 a

Network

NetworkManager

nmtui is a GUI-tool for managing NetworkManager connections.

Checks

# Show all active network connections
nmcli connection show

# Show connection information for interface ens5
nmcli connection show ens5

# Show active and unactive network connections
nmcli dev status

nmcli

# Bring logical interface ens6 up
nmcli device up ens6

# Turn off DHCP
nmcli con mod ens6 ipv4.method manual
nmcli con mod ens6 connection.autoconnect yes

# Add an IP-address to interface ens6
nmcli connection modify ens6 ipv4.address "192.168.0.10/24"

# Add DNS-servers to interface ens6
nmcli connection modify ens6 ipv4.dns "8.8.8.8,1.1.1.1,196.168.0.1"

# Add a gateway to interface ens6
nmcli con mod ens6 ipv4.gateway "192.168.0.1"

# Add a default route to interface ens160
nmcli connection modify ens160 +ipv4.routes "0.0.0.0/0 192.168.3.100"

# Remove an IP-address from interface ens6
nmcli con mod ens6 -ipv4.addresses 192.168.0.11/24

# Apply changes to interface ens
nmcli device reapply ens6

RHEL

Generic Interface

BOOTPROTO=static for static address
BOOTPROTO=dhcp for DHCP 

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

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 DCHP interface
network:
    version: 2
    ethernets:
        ens4:
            # Some info about the Interface/why does it exist
            dhcp4: true
            match:
                macaddress: fa:16:3e:aa:bb:cc
            set-name: ens4

Generic DHCP Interfaces, but while ignoring the routes for an Interface and disabling DHCP on the other. 

network:
    version: 2
    ethernets:
        ens4:
            # Some info about the Interface/why does it exist
            dhcp4: true
            dhcp4-overrides:
              use-routes: false
            match:
                macaddress: fa:16:3e:aa:bb:cc
            set-name: ens4
        ens5:
            # Some info about the Interface/why does it exist
            dhcp4: no
            match:
                macaddress: fa:16:cc:dd:ee
            set-name: ens5
Generic static interface

You may have to disable automatic network-configuration: 

sudo bash -c 'echo "network: {config: disabled}" > /etc/cloud/cloud.cfg.d/99-disable-network-config.cfg'
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, 8.8.8.8]
           routes:
              - to: default
                via: 192.168.0.1
VLAN Interface
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: 192.168.2.1
        eno1.30:
            id: 30
            link: eno1
            addresses: [192.168.3.1/24]
Empty Interface
network:
  version: 2
  ethernets:
    eno2:
      dhcp4: false
      dhcp6: false

Interface files

Classic /etc/network/interfaces.d files i.e. /etc/network/interfaces.d/ens200.conf Otherwise use /etc/network/interfaces

Generic IPv4
# /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
Generic IPv6
# /etc/network/interfaces.d/ens3.conf
iface ens3 inet6 static
    address abcd:defg:0:1234:5123:abcd:abcd:1234
    netmask 48
    gateway abcd:defg::1
Bond
auto eno1
iface eno1 inet manual

auto eno2
iface eno2 inet manual

auto bond0
iface bond0 inet static
        address 192.168.39.245
        gateway 192.168.39.254
        network 255.255.255.0
        bond-slaves eno1 eno2
        bond-miimon 100
        bond-mode 802.3ad
        bond-xmit-hash-policy layer2+3
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