Network management in Linux(CentOS/Red Hat)

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Really thanks to you for your interest in this topics. :)

IPV4 (LAN/MAN/WAN) : Network management

Generally, The IP address are classified in this way. These are the most common types. Although there are also CLASS D and CLASS E for research and reserve. The ranges are given below:

Class A: 0.0.0.0 – 126.255.255.255

Class B: 128.0.0.0 – 191.255.255.255

Class C: 192.0.0.0 – 223.255.255.255

 

 

[root@desktopX ~]# ip link

[root@desktopX ~]# ip addr show         ; CMD or GUI

[root@desktopX ~]# ifconfig             ; (active)

[root@desktopX ~]# ifconfig -a         ; all

 

[root@desktopX ~]# ifconfig br0 ; sepecific LAN (br0, eth0, ens33, enp2s0)

Linux (RHEL/CentOS-7)

Physical NIC : enp2s0 or ens33 (generally, starts with ‘en’)

Virtual Machine NIC: eth0

Virtual IP: enp2s0:1 or ens33:1 or eth0:1

loopback: lo

Bridge : br0

Wireless: wl

VMware NIC: eno16777736 – ethernet card information

 

Check Physical Connectivity:

[root@desktopX ~]# ip link

[root@desktopX ~]# mii-tool enp2s0   ;(physical Machine)

 

enp2s0 : negotiated 1000baseT-FD flow-control, link ok

enp2s0 : no link (not connected)

 

Host Name Configure (server)

[root@localhost ~]# hostname

 

[root@localhost ~]# vim /etc/hostname

serverX.example.com

 

[root@localhost ~]# logout  ;(ctrl+d)

[root@localhost ~]# reboot   ;(if required)

 

or

 

[root@localhost ~]# hostname

[root@localhost ~]# hostnamectl status

[root@localhost ~]# hostnamectl –static set-hostname serverX.example.com

[root@localhost ~]# reboot

 

[root@serverX ~]# ip link

[root@serverX ~]# ip addr

 

ether 8C:89:A5:E4:F3:64 => MAC

inet addr:172.25.11.X => IP Address

Bcast:172.25.11.255

Mask:255.255.255.0

inet6 addr: IPv6 Link Local address

 

[root@serverX ~]# ifconfig

 

N.B: (For Command Mode)

 

[root@serverX ~]# yum install net-tools -y (#ifconfig)

[root@serverX ~]# yum install setuptool -y   (GUI interface)

 

IP Configure

=> Tempoary (IP remove after system reboot)

=> Parmanet

 

Temporary IP Address Configure:

[root@serverX ~]# ifconfig

[root@serverX ~]# ifconfig eth1 172.25.11.200+X

[root@serverX ~]# ifconfig eth1 172.25.11.200+X netmask 255.255.255.0

[root@serverX ~]# ifconfig

 

[root@serverX ~]# ifconfig

 

Test the gateway:

[root@serverX ~]# ping 172.25.11.1

64 bytes from 172.25.11.1 : icmp_seq=1 ttl=64 time=0.451 ms

64 bytes from 172.25.11.1 : icmp_seq=2 ttl=64 time=0.317 ms

C^

 

[root@serverX ~]# ping -c 4 172.25.11.1

 

Check Default Gateway:

[root@serverX ~]# route -n

[root@serverX ~]# route add default gw 172.25.11.254

[root@serverX ~]# echo nameserver 8.8.8.8 > /etc/resolv.conf

[root@serverX ~]# echo nameserver 4.2.2.2 >> /etc/resolv.conf

[root@serverX ~]# cat /etc/resolv.conf

[root@serverX ~]# ping www.google.com

 

Delete:

[root@serverX ~]# route del default gw 172.25.11.254

[root@serverX ~]# route -n

 

[root@serverX ~]# reboot

 

IP Client Configure

=> Static

=> dhcp : autmatically ip configure

 

[root@serverX ~]# systemctl stop NetworkManager.service

[root@serverX ~]# systemctl disable NetworkManager.service

[root@serverX ~]# systemctl status NetworkManager.service

 

Static (parmanent) IP configure:

[root@serverX ~]# ifconfig eth0           ; notedown eth0 ether(MAC) Address

 

[root@serverX ~]# cd /etc/sysconfig/network-scripts/

[root@serverX network-scripts]# ls

[root@serverX network-scripts]# vim ifcfg-eth0

 

DEVICE=eth0                   ; no change

TYPE=Ethernet                 ; no change

HWADDR=AA:BB:CC:DD:EE:FF     ; no change

BOOTPROTO=none               ; none/static=static, dhcp for dynamic

IPADDR=X.X.X.X   (172.25.11.200+X) ;X is your IP address

NETMASK=Y.Y.Y.Y   (255.255.255.0)

GATEWAY=X.X.X.G   (172.25.11.1)

DNS1=A.A.A.A     (4.2.2.2)

DNS2=B.B.B.B    (8.8.8.8)

ONBOOT=yes                   ; Check that it is yes or not. must yes

 

[root@serverX network-scripts]# systemctl restart network.service

[root@serverX network-scripts]# systemctl enable network.service

 

[root@serverX network-scrip]# ifconfig

 

[root@serverX network-scrip]# ifup eth0

 

[root@serverX network-scrip]# ifconfig

 

[root@serverX ~]# ping 172.25.11.254 or ping 172.25.11.1

 

Enable and Disable:

[root@desktopX ~]# ifdown eth0

 

[root@desktopX ~]# ifconfig

 

[root@desktopX ~]# ifup eth0

 

[root@desktopX ~]# ifconfig

 

Working with Network Manager:

[root@serverX ~]# systemctl restart NetworkManager

[root@serverX ~]# systemctl enable NetworkManager

 

[root@serverX ~]# nmcli connection show

 

[root@serverX ~]# nmcli con del ‘eth1’

[root@serverX ~]# systemctl restart NetworkManager

 

[root@serverX ~]# nmcli connection show

NAME                     UUID                                    TYPE       DEVICE

Wired connection 1 5fb06bd0-0bb0-7ffb-45f1-d6edd65f3e03 802-3-ethernet       eth1

 

[root@localhost ~]# nmcli connection mod ‘Wired connection 1’ ipv4.addresses

192.168.11.200+X/24

[root@localhost ~]# nmcli con mod ‘Wired connection 1’ ipv4.gateway 192.168.2.1

 

[root@localhost ~]# nmcli connection mod ‘Wired connection 1’ ipv4.method manual

[root@localhost ~]# nmcli connection up “Wired connection 1”

[root@localhost ~]# ip addr