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How to Configure Your NIC for OVHcloud Link Aggregation in CentOS 7

Enable OVHcloud Link Aggregation in your CentOS 7 server

Last updated October 24th, 2019

Objective

OVHcloud Link Aggregation (OLA) technology is designed by our teams to increase your server’s availability, and boost the efficiency of your network connections. In just a few clicks, you can aggregate your network cards and make your network links redundant. This means that if one link goes down, traffic is automatically redirected to another available link. In this article, we will discuss how to bond your NICs to use them for OLA in CentOS 7.

Requirements

How to Configure Your NIC for OVHcloud Link Aggregation in the OVHcloud Manager

Instructions

Because we have a private-private configuration for our NICs in OLA, we will be unable to SSH into the server. Thus, we will need to leverage the IPMI tool to access the server. To do so, first log in to the OVHcloud Manager. Then select the server you wish to configure on the left-hand sidebar and click the IPMI tab.

remote_kvm

Next, click the From a Java applet (KVM) button. A JNLP program will download. Open the program to enter the IPMI. Log in using valid credentials for the server.

By default, using an OVHcloud template, the NICs will be named eth0 and eth1. If you are not using an OVHcloud template, you can find the names of your interfaces using the following command:

ip a

This command will yield numerous "interfaces." If you are having trouble determining which ones are your physical NICs, the first interface will still have the server's public IP address attached to it by default.

Once we have determined the names of our two NICs, we will configure NIC bonding in the OS. The first step is to create a bond interface. To do so, create the following configuration file in a text editor of your choice:

vi /etc/sysconfig/network-scripts/ifcfg-bond0

This will open an empty text file. To configure the bond interface, insert the following into the text file:

DEVICE=bond0
TYPE=Bond
NAME=bond0
BOOTPROTO=none
ONBOOT=yes
BONDING_MASTER=yes
IPADDR=10.0.0.1
NETMASK=255.255.255.0
BONDING_OPTS="mode=802.3ad miimon=100"

You can use any private IP address and subnet you wish you to use.

Save and exit the file once you have confirmed that the information is correct. Next, we need to configure both physical interfaces. By default, on an OVHcloud server, only eth0 will have a configuration file. Open it using the following command:

vi /etc/sysconfig/network-scripts/ifcfg-eth0

By default, the file will appear as follows:

DEVICE=eth0
BOOTPROTO=static
IPADDR=203.0.113.1
NETMASK=255.255.255.0
ONBOOT=yes
GATEWAY=203.0.113.254
IPV6INIT=yes
IPV6_AUTOCONF=no
IPV6ADDR=2001:0db8:0000:0001::/64

The IP addresses will be different for each server.

We will change the file to appear as follows:

DEVICE=eth0
BOOTPROTO=static
#IPADDR=203.0.113.1
#NETMASK=255.255.255.0
ONBOOT=yes
#GATEWAY=203.0.113.254
#IPV6INIT=yes
#IPV6_AUTOCONF=no
#IPV6ADDR=2001:0db8:0000:0001::/64
TYPE=Ethernet
HWADDR=00:53:00:00:00:00
MASTER=bond0
SLAVE=yes

The hardware address (MAC address) of the NIC can be found using the ip a command that we used earlier. It will be the number next to "link/ether" in the output.

The # in front of a line means that the server will ignore this line when reading the file. Thus, we will ignore these lines entirely when creating our interface file for eth1. We will create the eth1 configuration file using the following command:

vi /etc/sysconfig/network-scripts/ifcfg-eth1

This time, the file will be blank so add the following content to the file:

DEVICE=eth1
BOOTPROTO=static
ONBOOT=yes
TYPE=Ethernet
HWADDR=00:53:00:00:00:01
MASTER=bond0
SLAVE=yes

Finally, we will restart the network daemon using the following command:

systemctl restart network

To test that our bond is working, ping another server on the same vRack. If it works, you are all set. If it does not, double-check your configurations or try rebooting the server.

Conclusion

OVHcloud gives our customers the freedom and flexibility to leverage their hardware in the way that best fits their needs. Now that you have read this article, you should be able to configure OVHcloud Link Aggregation (OLA) in CentOS 7 in order to use both of your NICs as bonded private interfaces.


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