Configure an ENI

Procedure

1. View and record information of ENIs. For more information, see the Preparations section.
2. Use one of the following methods to configure ENIs based on the operating systems of your instances:
   • Alibaba Cloud Linux 2: Configure ENIs for instances that run Alibaba Cloud Linux 2
   • CentOS or Red Hat: Configure ENIs for instances that run CentOS or Red Hat
   • Ubuntu or Debian: Configure ENIs for instances that run Ubuntu or Debian
   • SUSE or openSUSE: Configure ENIs for instances that run SUSE or openSUSE
3. Configure routes for ENIs. For more information, see Configure routes for ENIs.

Preparations

You must query the attributes of each ENI, including the primary private IP address, subnet mask, default route, and MAC address. You must also pay attention to the mapping between the ENI name and the MAC address in subsequent configurations.

1. Remotely connect to an ECS instance. For more information, see OverviewGuidelines on instance connection.
2. Query the attributes of each ENI, including the primary private IP address, subnet mask, default route, and MAC address.
   • Method 1: Query the attributes in the ECS console.
     1. Log on to the ECS console.
     2. In the left-side navigation pane, choose Network & Security > ENIs.
     3. On the Network Interfaces page, find the ENIs whose attributes you want to query and view their primary private IP addresses and MAC addresses in the Private IP Address and Type/MAC Address(All) columns.
   • Method 2: Run the curl command to query the attributes from the instance metadata. For more information, see Overview of instance metadata.

     [root@LocalHost ~]# curl http://100.100.100.200/latest/meta-data/network/interfaces/macs/
     00:16:3e:12:e7:**/
     00:16:3e:12:16:**/
     [root@LocalHost ~]# curl http://100.100.100.200/latest/meta-data/network/interfaces/macs/00:16:3e:12:e7:**/netmask
     255.255.255.0
     [root@LocalHost ~]# curl http://100.100.100.200/latest/meta-data/network/interfaces/macs/00:16:3e:12:e7:**/primary-ip-address
     10.0.0.20
     [root@LocalHost ~]# curl http://100.100.100.200/latest/meta-data/network/interfaces/macs/00:16:3e:12:e7:**/gateway
     10.0.0.253

   • Method 3: Call the DescribeNetworkInterfaces operation to query the attributes.
   In this example, the following ENI information is returned:

   eth1 10.0.0.20/24 10.0.0.253 00:16:3e:12:e7:**
   eth2 10.0.0.21/24 10.0.0.253 00:16:3e:12:16:**

Configure ENIs for instances that run Alibaba Cloud Linux 2

eth1 is used in the following example. If you want to configure another ENI, modify the ENI ID.

1. Open the configuration file of the ENI.

   vi /etc/systemd/network/60-eth1.network

2. Press the I key to enter the edit mode and add the configuration information to the ENI configuration file.
   Choose one of the following configuration information sets based on your needs.

   • Scenario 1: Assign a dynamic IP address for the ENI over DHCP.

     Sample code:

     [Match]
     Name=eth1 # Specify the ENI to be configured.
     
     [Network]
     DHCP=yes
     
     [DHCP]
     UseDNS=yes

   • Scenario 2: Assign a static IP address for the ENI.

     Sample code:

     [Match]
     Name=eth1 # Specify the ENI to be configured.
     
     [Network]
     Address=192.168. **. **/24 # Specify the static IP address and subnet mask to be assigned.

   Press the Esc key, enter :wq, and then press the Enter key to save the file and exit the edit mode.
3. Check the ENI configuration file and confirm the modification.

   cat /etc/systemd/network/60-eth1.network

4. Restart the network service.

   systemctl restart systemd-networkd

Configure ENIs for instances that run CentOS or Red Hat

eth1 is used in the following example. If you want to configure another ENI, modify the ENI ID.

1. Download the multi-nic-util tool.

   wget https://image-offline.oss-cn-hangzhou.aliyuncs.com/multi-nic-util/multi-nic-util-0.6.tgz

2. Decompress the package and install the multi-nic-util tool.

   tar -zxvf multi-nic-util-0.6.tgz
   cd multi-nic-util-0.6
   bash install.sh

3. Restart ENI.

   systemctl restart eni.service

Method 2: Manually configure the ENI.

1. Open the configuration file of the ENI.

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

2. Press the I key to enter the edit mode and add the configuration information to the ENI configuration file.
   Sample code:

   DEVICE=eth1  # Specify the ENI to be configured.
   BOOTPROTO=dhcp
   ONBOOT=yes
   TYPE=Ethernet
   USERCTL=yes
   PEERDNS=no
   IPV6INIT=no
   PERSISTENT_DHCLIENT=yes
   HWADDR=00:16:3e:12:e7:**  # Specify this address as the queried MAC address of the ENI.
   DEFROUTE=no  # Specify that the ENI is not the default route. To prevent the active default route of the ECS instance from being changed when you start the ENI by running the ifup command, do not set eth1 to the default route.

   Press the Esc key, enter :wq, and then press the Enter key to save the file and exit the edit mode.
3. Check the ENI configuration file and confirm the modification.

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

4. Run the service network restart or systemctl restart network command to restart the network service.

Configure ENIs for instances that run Ubuntu or Debian

You can perform the following operations on instances that run Ubuntu 14.04, Ubuntu 16.04, or Debian:

1. Open the configuration file of an ENI.

   vi /etc/network/interfaces

2. Press the I key to enter the edit mode and add the configuration information to the ENI configuration file.
   eth1 is used in this example:

   auto eth0
   iface eth0 inet dhcp
   
   auto eth1  # Specify the ENI to be configured.
   iface eth1 inet dhcp

   Press the Esc key, enter :wq, and then press the Enter key to save the file and exit the edit mode.
3. Check the ENI configuration file and confirm the modification.

   cat /etc/network/interfaces

4. Run the service networking restart or systemctl restart networking command to restart the network service.

You can perform the following operations on instances that run Ubuntu 18.04:

1. Create and edit the configuration file of an ENI.
   eth1 is used in this example:

   vi /etc/netplan/eth1-netcfg.yaml

2. Press the I key to enter the edit mode and add the configuration information to the ENI configuration file.
   eth1 is used in this example:

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

   Press the Esc key, enter :wq, and then press the Enter key to save the file and exit the edit mode.

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

   • The configuration file is in the YAML format. Therefore, you must follow the YAML syntax rules when you configure the file.
   • You cannot use tabs for indentation in YAML files. Use the space instead.
   • We recommend that you copy information in the default /etc/netplan/99-netcfg.yaml configuration file to avoid format issues.
3. Check the ENI configuration file and confirm the modification.

   cat /etc/netplan/eth1-netcfg.yaml

4. Run the netplan apply command to make the configuration take effect.

Configure ENIs for instances that run SUSE or openSUSE

eth1 is used in the following example. If you want to configure another ENI, modify the ENI ID.

1. Open the configuration file of the ENI.

   vi /etc/sysconfig/network/ifcfg-eth1

2. Press the I key to enter the edit mode and add the configuration information to the ENI configuration file.

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

   Press the Esc key, enter :wq, and then press the Enter key to save the file and exit the edit mode.
3. Check the ENI configuration file and confirm the modification.

   cat /etc/sysconfig/network/ifcfg-eth1

4. Run the service network restart or systemctl restart network command to restart the network service.

Configure routes for ENIs

1. Start ENIs.
   1. Run the ifup <ENI name> command to start the dhclient process and initiate a DHCP request.

      ifup eth1
      ifup eth2

   2. Check the allocation of IP addresses. The result must be the same as the ENI information that you queried in the "Preparations" section.

      [root@ecshost~ ]# ip a
      1: lo:  mtu 65536 qdisc noqueue state UNKNOWN qlen 1
      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
      2: eth0:  mtu 1500 qdisc pfifo_fast state UP qlen 1000
      link/ether 00:16:3e:0e:16:** brd ff:ff:ff:ff:ff:ff
      inet 10.0.0.19/24 brd 10.0.0.255 scope global dynamic eth0
      valid_lft 31506157sec preferred_lft 31506157sec
      3: eth1:  mtu 1500 qdisc pfifo_fast state UP qlen 1000
      link/ether 00:16:3e:12:e7:** brd ff:ff:ff:ff:ff:ff
      inet 10.0.0.20/24 brd 10.0.0.255 scope global dynamic eth1
      valid_lft 31525994sec preferred_lft 31525994sec
      4: eth2:  mtu 1500 qdisc pfifo_fast state UP qlen 1000
      link/ether 00:16:3e:12:16:** brd ff:ff:ff:ff:ff:ff
      inet 10.0.0.21/24 brd 10.0.0.255 scope global dynamic eth2
      valid_lft 31526009sec preferred_lft 31526009sec

2. Set the metric parameter of the default route for each ENI in the route table.
   1. Set the metric parameter.

      ip -4 route add default via 10.0.0.253 dev eth1 metric 1001
      ip -4 route add default via 10.0.0.253 dev eth2 metric 1002

      The preceding commands set the metric parameter of eth1 and eth2 to the following values:

      eth1: gw: 10.0.0.253 metric: 1001
      eth2: gw: 10.0.0.253 metric: 1002

   2. Check whether the configuration succeeds. Pay attention to whether information of the Gateway and Metric columns is the same as the configured information.

      [root@ecshost~ ]# route -n
      Kernel IP routing table
      Destination Gateway Genmask Flags Metric Ref Use Iface
      0.0.0.0 10.0.0.253 0.0.0.0 UG 0 0 0 eth0
      0.0.0.0 10.0.0.253 0.0.0.0 UG 1001 0 0 eth1
      0.0.0.0 10.0.0.253 0.0.0.0 UG 1002 0 0 eth2
      10.0.0.0 0.0.0.0 255.255.255.0 U 0 0 0 eth0
      10.0.0.0 0.0.0.0 255.255.255.0 U 0 0 0 eth1
      10.0.0.0 0.0.0.0 255.255.255.0 U 0 0 0 eth2
      169.254.0.0 0.0.0.0 255.255.0.0 U 1002 0 0 eth0
      169.254.0.0 0.0.0.0 255.255.0.0 U 1003 0 0 eth1
      169.254.0.0 0.0.0.0 255.255.0.0 U 1004 0 0 eth2

3. Create route tables.
   1. Create the route tables.

      ip -4 route add default via 10.0.0.253 dev eth1 table 1001
      ip -4 route add default via 10.0.0.253 dev eth2 table 1002

      Note We recommend that you keep the names of the route tables the same as the metric values of the default routes. 1001 and 1002 are used in this example.
   2. Check whether the route tables are created.

      [root@ecshost~ ]# ip route list table 1001
      default via 10.0.0.253 dev eth1
      [root@ecshost~ ]# ip route list table 1002
      default via 10.0.0.253 dev eth2

4. Configure policy-based routing.
   1. Create policy-based routes.

      ip -4 rule add from 10.0.0.20 lookup 1001
      ip -4 rule add from 10.0.0.21 lookup 1002

   2. View routing rules.

      [root@ecshost~ ]# ip rule list
      0: from all lookup local
      32764: from 10.0.0.21 lookup 1002
      32765: from 10.0.0.20 lookup 1001
      32766: from all lookup main
      32767: from all lookup default