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Assiging Virtual IP to Server [Centos 6.5]

Creating Virtual Interface and Assign Multiple IP Addresses

Current IP of the server : 10.130.18.11.
Virtual IPs being assigned to server : 10.130.18.22, 10.130.18.23, 10.130.18.24 to our server..
Go to network-scripts directory and copy the existing ifcfg-eth0 file.
Make sure you are using a static ip for your server. 
 cd /etc/sysconfig/network-scripts/
static ip assigned scripts looks as below.
 [ahmed@ahmed-server network-scripts]$ sudo vim ifcfg-eth0

 DEVICE="eth0"
 BOOTPROTO=static
 NM_CONTROLLED="no"
 ONBOOT=yes
 TYPE="Ethernet"
 IPADDR=10.130.18.11
 NETMASK=255.255.255.192
 GATEWAY=10.138.18.1
 HWADDR=A0:0C:29:28:A7:4C
Make sure we copy the same script as ifcfg-eth0:0/1/2 
 sudo cp ifcfg-eth0 ifcfg-eth0:0
 sudo cp ifcfg-eth0:0 ifcfg-eth0:1
 sudo cp ifcfg-eth0:0 ifcfg-eth0:2
Change the copied script as below.
Here we are assigned the Virtual IP addresses to the Server.

ifcfg-eth0:0 Configuration

 [ahmed@ahmed-server network-scripts]$ sudo vim ifcfg-eth0:0

 DEVICE="eth0:0"
 BOOTPROTO=static
 NM_CONTROLLED="no"
 ONBOOT=yes
 TYPE="Ethernet"
 IPADDR=10.130.18.22
 NETMASK=255.255.255.192
 GATEWAY=10.138.18.1
 HWADDR=A0:0C:29:28:A7:4C

ifcfg-eth0:1 Configuration

 [ahmed@ahmed-server network-scripts]$ sudo vim ifcfg-eth0:1

 DEVICE="eth0:1"
 BOOTPROTO=static
 NM_CONTROLLED="no"
 ONBOOT=yes
 TYPE="Ethernet"
 IPADDR=10.130.18.23
 NETMASK=255.255.255.192
 GATEWAY=10.138.18.1
 HWADDR=A0:0C:29:28:A7:4C

ifcfg-eth0:2 Configuration

 [ahmed@ahmed-server network-scripts]$ sudo vim ifcfg-eth0:2

 DEVICE="eth0:2"
 BOOTPROTO=static
 NM_CONTROLLED="no"
 ONBOOT=yes
 TYPE="Ethernet"
 IPADDR=10.130.18.24
 NETMASK=255.255.255.192
 GATEWAY=10.138.18.1
 HWADDR=A0:0C:29:28:A7:4C
Now lets restart the network so that the changes take affect. 
 [ahmed@ahmed-server network-scripts]$ sudo /etc/init.d/network restart
 Shutting down interface eth0:                              [  OK  ]
 Shutting down loopback interface:                          [  OK  ]
 Bringing up loopback interface:                            [  OK  ]
 Bringing up interface eth0:  Determining if ip address 10.130.18.11 is already in use for device eth0...
                                                            [  OK  ]
Checking the configuration. 
 [ahmed@ahmed-server network-scripts]$ ifconfig
 eth0      Link encap:Ethernet  HWaddr A0:0C:29:28:A7:4C
           inet addr:10.130.18.11  Bcast:10.130.18.63  Mask:255.255.255.192
           inet6 addr: fe80::a2d3:c1ff:fef9:d8dc/64 Scope:Link
           UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
           RX packets:74 errors:0 dropped:0 overruns:0 frame:0
           TX packets:56 errors:0 dropped:0 overruns:0 carrier:0
           collisions:0 txqueuelen:1000
           RX bytes:6687 (6.5 KiB)  TX bytes:10366 (10.1 KiB)
           Interrupt:32

 eth0:0    Link encap:Ethernet  HWaddr A0:0C:29:28:A7:4C
           inet addr:10.130.18.22  Bcast:10.130.18.63  Mask:255.255.255.192
           UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
           Interrupt:32

 eth0:1    Link encap:Ethernet  HWaddr A0:0C:29:28:A7:4C
           inet addr:10.130.18.23  Bcast:10.130.18.63  Mask:255.255.255.192
           UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
           Interrupt:32

 eth0:2    Link encap:Ethernet  HWaddr A0:0C:29:28:A7:4C
           inet addr:10.130.18.24  Bcast:10.130.18.63  Mask:255.255.255.192
           UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
           Interrupt:32
Let Ping those IPs.
 ahmed@ahmed-second-server:~# ping 10.130.18.11
 PING 10.130.18.11 (10.130.18.11) 56(84) bytes of data.
 64 bytes from 10.130.18.11: icmp_req=2 ttl=59 time=0.288 ms
 64 bytes from 10.130.18.11: icmp_req=3 ttl=59 time=0.962 ms
 64 bytes from 10.130.18.11: icmp_req=4 ttl=59 time=0.287 ms
 ^C
 --- 10.130.18.11 ping statistics ---
 4 packets transmitted, 3 received, 25% packet loss, time 3008ms
 rtt min/avg/max/mdev = 0.287/0.512/0.962/0.318 ms
 ahmed@ahmed-second-server:~# ping 10.130.18.22
 PING 10.130.18.22 (10.130.18.22) 56(84) bytes of data.
 64 bytes from 10.130.18.22: icmp_req=1 ttl=59 time=0.680 ms
 64 bytes from 10.130.18.22: icmp_req=2 ttl=59 time=1.67 ms
 64 bytes from 10.130.18.22: icmp_req=3 ttl=59 time=0.274 ms
 ^C
 --- 10.130.18.22 ping statistics ---
 3 packets transmitted, 3 received, 0% packet loss, time 2004ms
 rtt min/avg/max/mdev = 0.274/0.877/1.678/0.590 ms
 ahmed@ahmed-second-server:~# ping 10.130.18.23
 PING 10.130.18.23 (10.130.18.23) 56(84) bytes of data.
 64 bytes from 10.130.18.23: icmp_req=2 ttl=59 time=0.853 ms
 64 bytes from 10.130.18.23: icmp_req=3 ttl=59 time=0.626 ms
 64 bytes from 10.130.18.23: icmp_req=4 ttl=59 time=0.346 ms
 ^C
 --- 10.130.18.23 ping statistics ---
 4 packets transmitted, 3 received, 25% packet loss, time 3014ms
 rtt min/avg/max/mdev = 0.346/0.608/0.853/0.208 ms

Assign Multiple IP Address Range

If you would like to create a range of Multiple IP Addresses to a particular interface called “ifcfg-eth0“, we use “ifcfg-eth0-range0” and copy the contains of ifcfg-eth0 on it as shown below.
 [ahmed@ahmed-server network-scripts]$ sudo cp -p ifcfg-eth0 ifcfg-eth0-range0
Now open “ifcfg-eth0-range0” file and add “IPADDR_START” and “IPADDR_END” IP address range as shown below.
 [ahmed@ahmed-server network-scripts]# vi ifcfg-eth0-range0

 #DEVICE="eth0"
 #BOOTPROTO=static
 #NM_CONTROLLED="no"
 #ONBOOT=yes
 TYPE="Ethernet"
 IPADDR_START=10.130.18.22
 IPADDR_END=10.130.18.24
 IPV6INIT=no
Save it and restart/start network service
 [ahmed@ahmed-server network-scripts]$ sudo /etc/init.d/network restart
 Shutting down interface eth0:                              [  OK  ]
 Shutting down loopback interface:                          [  OK  ]
 Bringing up loopback interface:                            [  OK  ]
 Bringing up interface eth0:  Determining if ip address 10.130.18.11 is already in use for device eth0...
                                                            [  OK  ]
Checking the configuration. Verify that virtual interfaces are created with IP Address. 
 [ahmed@ahmed-server network-scripts]$ ifconfig
 eth0      Link encap:Ethernet  HWaddr A0:0C:29:28:A7:4C
           inet addr:10.130.18.11  Bcast:10.130.18.63  Mask:255.255.255.192
           inet6 addr: fe80::a2d3:c1ff:fef9:d8dc/64 Scope:Link
           UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
           RX packets:74 errors:0 dropped:0 overruns:0 frame:0
           TX packets:56 errors:0 dropped:0 overruns:0 carrier:0
           collisions:0 txqueuelen:1000
           RX bytes:6687 (6.5 KiB)  TX bytes:10366 (10.1 KiB)
           Interrupt:32

 eth0:0    Link encap:Ethernet  HWaddr A0:0C:29:28:A7:4C
           inet addr:10.130.18.22  Bcast:10.130.18.63  Mask:255.255.255.192
           UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
           Interrupt:32

 eth0:1    Link encap:Ethernet  HWaddr A0:0C:29:28:A7:4C
           inet addr:10.130.18.23  Bcast:10.130.18.63  Mask:255.255.255.192
           UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
           Interrupt:32

 eth0:2    Link encap:Ethernet  HWaddr A0:0C:29:28:A7:4C
           inet addr:10.130.18.24  Bcast:10.130.18.63  Mask:255.255.255.192
           UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
           Interrupt:32
More Info : 
 http://www.tecmint.com/create-multiple-ip-addresses-to-one-single-network-interface/
 http://linuxconfig.org/configuring-virtual-network-interfaces-in-linux
 http://www.jamescoyle.net/how-to/307-create-a-virtual-ip-address-in-linux
 https://myunixlab.wordpress.com/2011/02/04/how-to-add-virtual-ip-address-in-linux/
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