Some times you might want to use more than one IP address for your network interface card. What are you going to do? Buy an extra network card and assign new IP? No, It’s not necessary(atleast in the small networks). We can now assign multiple ip addresses to single network interface card in CentOS / RHEL 7 systems. Curious to know how? Well, Follow me, It is not that difficult.
First, let us find the IP address of the network card. In my CentOS 7 server, I use only one network card.
Run the following command with root user privileges:
ip addr
Sample output:
1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00 inet 127.0.0.1/8 scope host lo valid_lft forever preferred_lft forever inet6 ::1/128 scope host valid_lft forever preferred_lft forever 2: enp0s3: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UP qlen 1000 link/ether 08:00:27:80:63:19 brd ff:ff:ff:ff:ff:ff inet 192.168.1.150/24 brd 192.168.1.255 scope global enp0s3 valid_lft forever preferred_lft forever
As you see in the above output, my network card name is enp0s3, and its IP address is 192.168.1.150.
Well, as you may know, the the network card configuration files of your system is stored under /etc/sysconfig/network-scripts/ directory. Each cards details will be stored in different names, for example ifcfg-enp0s3.
Let us see the details of ifcfg-enp0s3.
cat /etc/sysconfig/network-scripts/ifcfg-enp0s3
Sample output:
TYPE="Ethernet" BOOTPROTO="none" DEFROUTE="yes" IPV4_FAILURE_FATAL="no" IPV6INIT="yes" IPV6_AUTOCONF="yes" IPV6_DEFROUTE="yes" IPV6_FAILURE_FATAL="no" NAME="enp0s3" UUID="e9f9caef-cb9e-4a19-aace-767c6ee6f849" ONBOOT="yes" HWADDR="08:00:27:80:63:19" IPADDR0="192.168.1.150" PREFIX0="24" GATEWAY0="192.168.1.1" DNS1="192.168.1.1" IPV6_PEERDNS="yes" IPV6_PEERROUTES="yes"
Okay, now we will assign multiple addresses in the same subnet.
Edit file /etc/sysconfig/network-scripts/ifcfg-enp0s3:
vi /etc/sysconfig/network-scripts/ifcfg-enp0s3
Add extra IP addresses one by one as shown below.
TYPE="Ethernet" BOOTPROTO="none" DEFROUTE="yes" IPV4_FAILURE_FATAL="no" IPV6INIT="yes" IPV6_AUTOCONF="yes" IPV6_DEFROUTE="yes" IPV6_FAILURE_FATAL="no" NAME="enp0s3" UUID="933cdc9b-b383-4ddd-b219-5a72c69c9cf0" ONBOOT="yes" HWADDR="08:00:27:3F:AB:68" IPADDR0="192.168.1.150" IPADDR1="192.168.1.151" IPADDR2="192.168.1.152" PREFIX0="24" GATEWAY0="192.168.1.1" DNS1="192.168.1.1" IPV6_PEERDNS="yes" IPV6_PEERROUTES="yes"
As you see above, I have added two more IP addresses: IPADDR1=”192.168.1.151″ & IPADDR2=”192.168.1.152″
Like wise, you can add as many a IP addresses you want.
Finally, save and close the file. Restart network service to take effect the changes.
systemctl restart network
Now, let us check the IP addresses have been added or not.
ip addr
Sample output:
: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00 inet 127.0.0.1/8 scope host lo valid_lft forever preferred_lft forever inet6 ::1/128 scope host valid_lft forever preferred_lft forever 2: enp0s3: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UP qlen 1000 link/ether 08:00:27:3f:ab:68 brd ff:ff:ff:ff:ff:ff inet 192.168.1.150/24 brd 192.168.1.255 scope global enp0s3 valid_lft forever preferred_lft forever inet 192.168.1.151/24 brd 192.168.1.255 scope global secondary enp0s3 valid_lft forever preferred_lft forever inet 192.168.1.152/24 brd 192.168.1.255 scope global secondary enp0s3 valid_lft forever preferred_lft forever inet6 fe80::a00:27ff:fe3f:ab68/64 scope link valid_lft forever preferred_lft forever
As you see above, the single network interface card has three IP addresses.
Let us ping the newly added IP addresses:
ping -c 4 192.168.1.151
Sample output:
PING 192.168.1.151 (192.168.1.151) 56(84) bytes of data. 64 bytes from 192.168.1.151: icmp_seq=1 ttl=64 time=0.048 ms 64 bytes from 192.168.1.151: icmp_seq=2 ttl=64 time=0.075 ms 64 bytes from 192.168.1.151: icmp_seq=3 ttl=64 time=0.077 ms 64 bytes from 192.168.1.151: icmp_seq=4 ttl=64 time=0.077 ms --- 192.168.1.151 ping statistics --- 4 packets transmitted, 4 received, 0% packet loss, time 2999ms rtt min/avg/max/mdev = 0.048/0.069/0.077/0.013 ms
ping -c 4 192.168.1.152
Sample output:
PING 192.168.1.152 (192.168.1.152) 56(84) bytes of data. 64 bytes from 192.168.1.152: icmp_seq=1 ttl=64 time=0.034 ms 64 bytes from 192.168.1.152: icmp_seq=2 ttl=64 time=0.075 ms 64 bytes from 192.168.1.152: icmp_seq=3 ttl=64 time=0.073 ms 64 bytes from 192.168.1.152: icmp_seq=4 ttl=64 time=0.075 ms --- 192.168.1.152 ping statistics --- 4 packets transmitted, 4 received, 0% packet loss, time 2999ms rtt min/avg/max/mdev = 0.034/0.064/0.075/0.018 ms
If you want to use different subnet, then you can change the PREFIX0=24 line to different subnet, such as PREFIX1=16.
For example, I am going to add Class A IP address(ex.10.0.0.1) to my network card.
TYPE="Ethernet" BOOTPROTO="none" DEFROUTE="yes" IPV4_FAILURE_FATAL="no" IPV6INIT="yes" IPV6_AUTOCONF="yes" IPV6_DEFROUTE="yes" IPV6_FAILURE_FATAL="no" NAME="enp0s3" UUID="933cdc9b-b383-4ddd-b219-5a72c69c9cf0" ONBOOT="yes" HWADDR="08:00:27:3F:AB:68" IPADDR0="192.168.1.150" IPADDR1="192.168.1.151" IPADDR2="192.168.1.152" IPADDR3="10.0.0.1" PREFIX0="24" PREFIX1=16 GATEWAY0="192.168.1.1" DNS1="192.168.1.1" IPV6_PEERDNS="yes" IPV6_PEERROUTES="yes"
Do you notice that I have added a Class A type address(10.0.0.1) and prefix=16.
Save and close the file. Restart network service,
Then, ping the new added IP:
ping -c 4 10.0.0.1
Sample output:
PING 10.0.0.1 (10.0.0.1) 56(84) bytes of data. 64 bytes from 10.0.0.1: icmp_seq=1 ttl=64 time=0.097 ms 64 bytes from 10.0.0.1: icmp_seq=2 ttl=64 time=0.073 ms 64 bytes from 10.0.0.1: icmp_seq=3 ttl=64 time=0.074 ms 64 bytes from 10.0.0.1: icmp_seq=4 ttl=64 time=0.075 ms --- 10.0.0.1 ping statistics --- 4 packets transmitted, 4 received, 0% packet loss, time 3000ms rtt min/avg/max/mdev = 0.073/0.079/0.097/0.014 ms
Similarly, you can add different Gateways too.
Want to know how to add additional IP addresses on CentOS/RHEL/Scientific Linux/Fedora systems, check the following link.
That’s it.
