Assign multiple IP addresses to a network card on CentOS 7
Sometimes you may want to give a network card more than one address. What should you do? Also buy a network card to allocate addresses? In a small network there is actually no need to do this. We can now assign multiple ip addresses to a network card in CentOS/RHEL 7. Want to know how? OK, follow me, it's not that hard.
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First, let's 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 privileges:
ip addr
Example 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 forever2: 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 can see above, my network card name is enp0s3, and the ip address is 192.168.1.150.
As you know, network card configuration files are stored in /etc/sysconfig/network-scripts/ directory. The details of each NIC will be stored with a different name, such as ifcfg-enp0s3.
Let's look at the details of ifcfg-enp0s3:
cat /etc/sysconfig/network-scripts/ifcfg-enp0s3
Example 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"
Ok, 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 additional IP addresses like this:
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 can see, I have added two IP addresses:
IPADDR1=”192.168.1.151″ & IPADDR2=”192.168.1.152″.
Similarly, you can add more ip addresses.
Finally, save and exit the file. Restart network services for the changes to take effect.
systemctl restart network
Now, let's check if the ip address has been added.
ip addr
Example 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 forever2: 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 can see, a single network card already has 3 ip addresses.
Let's ping the newly added IP address:
ping -c 4 192.168.1.151
Example 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 ms64 bytes from 192.168.1.151: icmp_seq=2 ttl=64 time=0.075 ms64 bytes from 192.168.1.151: icmp_seq=3 ttl=64 time=0.077 ms64 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 2999msrtt min/avg/max/mdev = 0.048/0.069/0.077/0.013 ms
ping -c 4 192.168.1.152
Example 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 ms64 bytes from 192.168.1.152: icmp_seq=2 ttl=64 time=0.075 ms64 bytes from 192.168.1.152: icmp_seq=3 ttl=64 time=0.073 ms64 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 2999msrtt min/avg/max/mdev = 0.034/0.064/0.075/0.018 ms
If you want to use a different subnet, you have to change PREFIX0=24 to a different subnet, eg PREFIX1=16.
For example, I want to add a class A address (*such as 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=16GATEWAY0="192.168.1.1"DNS1="192.168.1.1"IPV6_PEERDNS="yes"IPV6_PEERROUTES="yes"
You can see that I have added a class A address (10.0.0.1) with a prefix of 16.
Save and exit the file. Restart the network service, then, ping the newly added address:
ping -c 4 10.0.0.1
Example 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 ms64 bytes from 10.0.0.1: icmp_seq=2 ttl=64 time=0.073 ms64 bytes from 10.0.0.1: icmp_seq=3 ttl=64 time=0.074 ms64 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 3000msrtt min/avg/max/mdev = 0.073/0.079/0.097/0.014 ms