Elastic Compute Service:Configure a secondary ENI

(Recommended) Obtain information about the secondary ENI in the ECS console

1. Log on to the ECS console.

2. In the left-side navigation pane, choose Network & Security > Elastic Network Interfaces.

3. In the top navigation bar, select the region and resource group to which the resource belongs.

4. On the Elastic Network Interfaces page, find the secondary ENI whose information you want to obtain and view the primary private IP address and MAC address in the IP Address and MAC Address columns.

Obtain information about the secondary ENI from instance metadata

1. Connect to the Linux ECS instance.

   For more information, see Connect to a Linux instance by using a password or key.

2. Run the following commands in sequence to obtain the information of the secondary ENI.

   • Obtain the MAC addresses of all ENIs that are bound to the Linux instance.

     curl http://100.100.100.200/latest/meta-data/network/interfaces/macs/

     Note

     The MAC addresses of the ENIs are required to obtain the primary private IP addresses, subnet masks, and gateway addresses of the ENIs.

   • Obtain the primary private IP address of a specific ENI.

     curl http://100.100.100.200/latest/meta-data/network/interfaces/macs/00:16:3e:19:**:**/primary-ip-address

   • Obtain the subnet mask of a specific ENI.

     curl http://100.100.100.200/latest/meta-data/network/interfaces/macs/00:16:3e:19:**:**/netmask

   • Obtain the gateway address of a specific ENI.

     curl http://100.100.100.200/latest/meta-data/network/interfaces/macs/00:16:3e:19:**:**/gateway

The following figure shows a sample command output. In the sample command output, 00:16:3e:16:**:** is the MAC address of the primary ENI and 00:16:3e:0f:**:** is the MAC address of the secondary ENI.

Alibaba Cloud Linux 2, CentOS 6, CentOS 7, or Red Hat

If the instance runs Alibaba Cloud Linux 2, CentOS 6, CentOS 7, or Red Hat, you can use the multi-nic-util tool to automatically configure or modify the configurations of ENIs that are bound to the instance.

(Recommended) Method 1: Use the multi-nic-util tool to configure a secondary ENI

1. Run the following commands to download and install the multi-nic-util tool:

wget https://image-offline.oss-cn-hangzhou.aliyuncs.com/multi-nic-util/multi-nic-util-0.6.tgz && \
tar -zxvf multi-nic-util-0.6.tgz && \
cd multi-nic-util-0.6 && \
bash install.sh

2. Run the following command to restart the ENI service:

   sudo systemctl restart eni.service

Method 2: Modify the configuration file of a secondary ENI to configure the secondary ENI

1. Run the following command to open the configuration file of the secondary ENI:

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

2. Press the I key to enter Insert mode and add the information about the secondary ENI to the configuration file. Press the Esc key to exit Insert mode and enter :wq to save and close the configuration file.

   Sample information about the secondary ENI:

   DEVICE=eth1  # Specify the name of the ENI that you want to configure. 
   BOOTPROTO=dhcp
   ONBOOT=yes
   TYPE=Ethernet
   USERCTL=yes
   PEERDNS=no
   IPV6INIT=no
   PERSISTENT_DHCLIENT=yes
   HWADDR=00:16:3e:0f:**:**  # Specify the MAC address of the ENI that you obtained. 
   DEFROUTE=no  # Indicates that the ENI is not used for the default route. To prevent the default route of the instance from being changed when you run the ifup command to start the secondary ENI, do not specify eth1 information as the default route.

3. Run one of the following commands to restart the network service:

   • Versions earlier than CentOS 7 and Red Hat 7, such as CentOS 6 and Red Hat 6:

   sudo service network restart

   • CentOS 7 or later, RedHat 7 or later, and Alibaba Cloud Linux 2:

   sudo systemctl restart network

Ubuntu or Debian

If the instance runs Ubuntu or Debian, modify the configuration file of the secondary ENI based on the image version.

• Ubuntu 14.04, Ubuntu 16.04, and Debian

  1. Run the following command to open the configuration file of the secondary ENI:

     vi /etc/network/interfaces

  2. Press the I key to enter Insert mode and add information about the secondary ENI to the configuration file. Then press the Esc key to exit Insert mode and enter :wq to save and close the configuration file.

     Sample information about the secondary ENI:

     auto eth0
     iface eth0 inet dhcp
     
     auto eth1  # Specify the name of the ENI that you want to configure. 
     iface eth1 inet dhcp

     Note

     The eth0 primary ENI is configured in the same configuration file in which the eth1 secondary ENI is configured. You must add information about the primary ENI to the configuration file.

  3. Run one of the following commands to restart the network service:

     • Ubuntu 14.04:

       sudo service networking restart

     • Ubuntu 16.04 and Debian:

       sudo systemctl restart networking

     The configurations of the secondary ENI take effect regardless of whether the following alert notification appears. You can run the ip address show command to check whether the IP address of the secondary ENI is recognized.

• Ubuntu 18.04, 20.04, 22.04, and 24.04

  Note

  By default, Ubuntu 20.04, 22.04, and 24.04 support automatic configuration for associated secondary ENIs. If the automatic configuration is failed, refer to the following steps for manual configuration.

  1. Run the following command to open the configuration file of the secondary ENI:

  vi /etc/netplan/eth1-netcfg.yaml

  2. Press the I key to enter Insert mode and add information about the secondary ENI to the configuration file. Press the Esc key to exit Insert mode and enter :wq to save and close the configuration file.

     Note

     When you modify the configuration file, take note of the following items:

     • The configuration file is in the YAML format. Follow the YAML syntax rules when you modify the configuration file.

     • Use spaces for indentation in YAML files. Tabs are not supported.

     • To prevent formatting issues, we recommend that you copy information from the default /etc/netplan/99-netcfg.yaml configuration file.

     Sample information about the secondary ENI:

     network:
       version: 2
       renderer: networkd
       ethernets:
         eth1:
           dhcp4: yes
           dhcp6: no

  3. Run the following command for the changes to the configuration file to take effect:

  netplan apply

SUSE or openSUSE

If your instance runs SUSE or openSUSE, you must modify the configuration file of the secondary ENI.

1. Run the following command to open the configuration file of the secondary ENI:

   vi /etc/sysconfig/network/ifcfg-eth1

2. Press the I key to enter Insert mode and add information about the secondary ENI to the configuration file. Press the Esc key to exit Insert mode and enter :wq to save and close the configuration file.

   In the following example, the IP address assignment method is set to Dynamic Host Configuration Protocol (DHCP):

   BOOTPROTO='dhcp4'
   STARTMODE='auto'
   USERCONTROL='no'

3. Run one of the following commands to restart the network service:

   • Versions earlier than SUSE Linux Enterprise Server 12 and openSUSE 13.2:

     sudo service network restart

   • SUSE Linux Enterprise Server 12 or later, and openSUSE 13.2 or later:

     sudo systemctl restart network

Configure routes for a secondary ENI on an instance that runs Alibaba Cloud Linux 2 or CentOS 7

1. Run the following command to query the route information:

   route -n

   Sample command outputs:

   • The following command output contains only the route information of the eth0 primary ENI. No routes are configured for the eth1 secondary ENI. You must perform subsequent operations to configure routes for the secondary ENI.

   • The following command output contains the route information of the eth0 primary ENI and the eth1 secondary ENI. You do not need to perform subsequent operations to configure routes for the secondary ENI. If the configured routes do not meet your business requirements, you can modify the route configurations.

2. Run the following commands to configure the default route:

   ip -4 route add default via 192.168.**.253 dev eth1 metric 1001 && \
   ip -4 route add default via 192.168.**.253 dev eth1 table 1001 && \
   ip -4 rule add from 192.168.**.*2 lookup 1001

   Note

   You can run the preceding commands to configure the default route for the eth1 secondary ENI, create a route table, and then attach a routing policy to the table. In this example, a route table named table 1001 is created. We recommend that the name of the route table is the same as the metric value in the default route of the ENI. 192.168.**.253 is the gateway address and 192.168.*.*2 is the primary private IP address of the eth1 secondary ENI. Replace the parameter values with actual values.

3. Run the following commands to query the created route table and routing policy:

   ip route list table 1001 && \
   ip rule list

   The following command output indicates that the route table and routing policy are created.

4. Configure routes to automatically update on instance startup.

   After you configure routes for the eth1 secondary ENI, you must configure the routes to automatically update on instance startup. Otherwise, the routes become invalid when the instance is restarted.

   1. Run the following command to open the /etc/rc.local file:

      vim /etc/rc.local

   2. Press the I key to enter Insert mode, add the following content, press the Esc key to exit Insert mode, and then enter :wq to save and close the file.

      ip -4 route add default via 192.168.**.253 dev eth1 metric 1001
      ip -4 route add default via 192.168.**.253 dev eth1 table 1001
      ip -4 rule add from 192.168.**.*2 lookup 1001

   3. Run the following command to grant execute permissions on the /etc/rc.local file:

      sudo chmod +x /etc/rc.local

Configure routes for a secondary ENI on an instance that runs CentOS 8

1. Run the following command to query the route information:

   route -n

   The following command output contains the route information of the eth0 primary ENI and the eth1 secondary ENI.

2. Create a script that is used to configure routes.

   1. Run the following command to create and open the /home/route.sh file:

      vi /home/route.sh

   2. Press the I key to enter Insert mode, add the following content, press the Esc key to exit Insert mode, and then enter :wq to save and close the file.

      Note

      The following sample script provides an example on how to create a route table and attach a routing policy to the route table for the eth1 secondary ENI. In this example, a route table named table 1001 is created, 192.168.**.253 is the gateway address, and 192.168.*.*2 is the primary private IP address of the eth1 secondary ENI.

      #!/bin/bash
      
      i=0
      while true; do
              /usr/sbin/ip -4 route add default via 192.168.**.253 dev eth1 table 1001
              if [ $? -eq 0 ]; then
                      break
          fi
              sleep 3
              let i++
              if [ $i -gt 10 ]; then
                      exit -1
              fi
      done
      
      i=0
      while true; do
              /usr/sbin/ip -4 rule add from 192.168.**.*2 lookup 1001
              if [ $? -eq 0 ]; then
                      break
          fi
              sleep 3
              let i++
              if [ $i -gt 10 ]; then
                      exit -1
              fi
      done

3. Run the following command to configure the default route:

   sh /home/route.sh

4. Run the following commands to query the created route table and routing policy:

   ip route list table 1001 && \
   ip rule list

   The following figure shows a sample command output.

5. Configure routes to automatically update on instance startup.

   After you perform the preceding steps to configure routes for the eth1 secondary ENI, you must perform the following steps to configure the routes to automatically update on instance startup. Otherwise, the routes become invalid after the instance is restarted.

   1. Run the following command to open the /etc/rc.local file:

      vim /etc/rc.local

   2. Press the I key to enter Insert mode, add the following content, press the Esc key to exit Insert mode, and then enter :wq to save and close the file.

      sh /home/route.sh

   3. Run the following command to grant execute permissions on the /etc/rc.local file:

      sudo chmod +x /etc/rc.local