Assign Multiple IP Address

• Assign Multiple IP Address to Single LAN Card is called IP Aliasing
• IP Aliasing is useful for create virtual websites on Apache or Nginx.
• The main advantage of IP Alias is, you don’t have to purchase new LAN Card for each ip address.

Setup Network Alias

• Let’s assume that we want to attach two ip address (192.168.0.10 & 192.168.0.11) to the eth0 NIC card.

/-----------------------------------------\
| Adaptor     IP Address        Type      |
|------------------------------------------
| eth0        192.168.0.9       Primary   |
| eth0:0      192.168.0.10      Alias 1   |
| eth0:1      192.168.0.11      Alias 2   |
\-----------------------------------------/

Temporary Setup

[mitesh@Matrix ~]$ sudo ifconfigeth0:0 192.168.0.10 up
[mitesh@Matrix ~]$ sudo ifconfigeth0:1 192.168.0.11 up

NOTE!: Above chnages lost when you restart system or reload/restart network service.

Permantly Setup

RedHat/CentOS

• Let’s copy the Primary NIC configuration file.

[mitesh@Matrix ~]$ cd /etc/sysconfig/network-scripts/
[mitesh@Matrix ~]$ cp -v ifcfg-eth0 ifcfg-eth0:0
[mitesh@Matrix ~]$ cp -v ifcfg-eth0 ifcfg-eth0:1

• Open ifcfg-eth0 and view the contents.

[mitesh@Matrix ~]$ cat /etc/sysconfig/network-scripts/ifcfg-eth0
DEVICE="eth0"
BOOTPROTO=static
ONBOOT=yes
TYPE="Ethernet"
IPADDR=192.168.0.9
NETMASK=255.255.255.0
GATEWAY=192.168.0.1
HWADDR=00:0B:42:28:AB:4B

• We have to modify DEVICE and IPADDR parameter for our virtual network interface (eth0:0 & eth0:1)

[mitesh@Matrix ~]$ cat /etc/sysconfig/network-scripts/ifcfg-eth0:0
DEVICE="eth0:0"
BOOTPROTO=static
ONBOOT=yes
TYPE="Ethernet"
IPADDR=192.168.0.10
NETMASK=255.255.255.0
GATEWAY=192.168.0.1
HWADDR=00:0B:42:28:AB:4B

[mitesh@Matrix ~]$ cat /etc/sysconfig/network-scripts/ifcfg-eth0:1
DEVICE="eth0:1"
BOOTPROTO=static
ONBOOT=yes
TYPE="Ethernet"
IPADDR=192.168.0.11
NETMASK=255.255.255.0
GATEWAY=192.168.0.1
HWADDR=00:0B:42:28:AB:4B

Debian/Ubuntu

• Open /etc/network/interfaces file and view the contents.

[mitesh@Matrix ~]$ cat /etc/network/interfaces
# The loopback network interface
auto lo
iface lo inet loopback

# The primary network interface
allow-hotplug eth0
#iface eth0 inet dhcp
iface eth0 inet static
 address  192.168.0.9
 netmask  255.255.255.0
 gateway  192.168.0.1
 dns-nameservers 8.8.8.8 8.8.4.4

• We have to add following line to setup virtual network interface (eth0:0 & eth0:1)

# Virtual Aliases
auto eth0:0
iface eth0:0 inet static
        address 192.168.0.10
        netmask 255.255.255.0

auto eth0:1
iface eth0:1 inet static
        address 192.168.0.11
        netmask 255.255.255.0

NOTE!: Once, you’ve made all changes, save all your changes and restart the network service for the changes to reflect.

Verify Network Alias

[mitesh@Matrix ~]$ ifconfig
eth0      Link encap:Ethernet  HWaddr 00:0B:42:28:AB:4B
          inet addr:192.168.0.9  Bcast:192.168.0.255  Mask:255.255.255.0
          inet6 addr: fe80::96de:80ff:fe63:ab6a/64 Scope:Link
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          RX packets:198507112 errors:0 dropped:0 overruns:0 frame:0
          TX packets:187207576 errors:0 dropped:0 overruns:0 carrier:1
          collisions:0 txqueuelen:1000
          RX bytes:96441149361 (89.8 GiB)  TX bytes:59909542838 (55.7 GiB)
          Interrupt:18

eth0:0    Link encap:Ethernet  HWaddr 00:0B:42:28:AB:4B
          inet addr:192.168.0.10  Bcast:192.168.0.255  Mask:255.255.255.0
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          Interrupt:18 Base address:0x2000

eth0:1    Link encap:Ethernet  HWaddr 00:0B:42:28:AB:4B
          inet addr:192.168.0.11  Bcast:192.168.0.255  Mask:255.255.255.0
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          Interrupt:18 Base address:0x2000