Centos7.6 dual network card configuration and switching test

**Foreword: **

​ In production, I received an alarm from the supervisor, and the network card of a server was switched back and forth, asking if it was abnormal. The reason is that when the server was in the test area, the dual network card mode was active-active, and it switched back and forth after it was in the production environment. This article simulates dual network card configuration and testing in an esxi environment.

**Environmental description: **

1. Constructing a dual network card test environment##

The system currently has only one network card, and a dual network card environment needs to be constructed.

1. Existing environment view###

Network card ifcfg-ens160 configuration:

[ root@client network-scripts]# more ifcfg-ens160
TYPE=Ethernet
PROXY_METHOD=none
BROWSER_ONLY=no
BOOTPROTO=static
DEFROUTE=yes
NAME=ens160
UUID=003981c1-76e4-4a67-9f84-f42cb033bbba
DEVICE=ens160
ONBOOT=yes
IPADDR=172.27.34.85
PREFIX=24
GATEWAY=172.27.34.1
IPV6_PRIVACY=no
DNS1=202.xxx.xxx.xxx

DNS fill in according to the actual situation

2. Add a new network card

The existing environment has only one network card

Add a network card

3. View newly added network card

Two, dual network card configuration##

1. New ifcfg-bond0

[ root@client network-scripts]# touch ifcfg-bond0
[ root@client network-scripts]# more ifcfg-bond0 
TYPE=Bond
BOOTPROTO=static
DEFROUTE=yes
DEVICE=bond0
USERCTL=no
ONBOOT=yes
IPADDR=172.27.34.85
PREFIX=24
GATEWAY=172.27.34.1
DNS1=202.xxx.xxx.xxx
BONDING_OPTS="miimon=100 mode=1"

Create a new network card file ifcfg-bond0 and configure it. mode=1: active/standby mode, only one network card works, when the main network card fails, it will switch to the standby network card; mode=0: [load balance] (https://cloud.tencent.com/product/clb?from=10680) mode, both network cards work, providing twice the bandwidth. The network card mode can be selected according to the actual production situation.

2. Configure network card ifcfg-ens160

[ root@client network-scripts]# more ifcfg-ens160
TYPE=Ethernet
BOOTPROTO=static
NAME=eno2
HWADDR=00:0c:29:c8:de:24
DEVICE=ens160
USERCTL=no
ONBOOT=yes
MASTER=bond0
SLAVE=yes

3. Configure ifcfg-ens190

[ root@client network-scripts]# touch ifcfg-ens190
[ root@client network-scripts]# more ifcfg-ens190 
TYPE=Ethernet
BOOTPROTO=static
NAME=eno2
HWADDR=00:0c:29:c8:de:2e
DEVICE=ens190
USERCTL=no
ONBOOT=yes
MASTER=bond0
SLAVE=yes

Create a new network card file ifcfg-ens190 and configure

4. Restart network###

[ root@client ~]# systemctl restart network

Restart network or host

5. View network

NIC bond0 has been tied to ip 172.27.34.85

Three, dual network card switch test##

1. Main network port view

[ root@client ~]#  cat /proc/net/bonding/bond0 

Dual network card mode is active and standby, the main network card is ens160

2. Close ens160

[ root@client ~]# ifdown ifcfg-ens160
Successfully disconnected the device'ens160'。
[ root@client ~]#  cat /proc/net/bonding/bond0    

At this time, the main network card is ens190, and the network connection is normal

3. Start ens160

[ root@client ~]# ifup ifcfg-ens160
The connection has been successfully activated (D-Bus activity path:/org/freedesktop/NetworkManager/ActiveConnection/11）
[ root@client ~]#  cat /proc/net/bonding/bond0      

Start ens160, the main network card is still ens190, and the network connection is normal

The test is complete, and the dual network card active/standby mode is valid.

**All scripts and configuration files in this article have been uploaded to github: **Centos7.6-for-Dual-network-card-settings