Configure an ENI

Prerequisite

You have attached an elastic network card to an ECS instance.

Procedure

To configure an ENI manually, follow these steps:

1. Use the DescribeNetworkInterfaces interface or log on to the ECS console to obtain the following attributes of the ENI: the primary private IP address, subnet mask, the default route, and the MAC address. To obtain these attributes in the ECS console, follow these steps:
   1. Log on to the  ECS console.
   2. Find the target ENI and obtain its primary private IP address, subnet mask, default route, and MAC address. Example:

      
      eth1 10.0.0.20/24 10.0.0.253 00: 16: 12: E7: 27
      eth2 10.0.0.21/24 10.0.0.253 00: 16: 12: 16: EC

2. Connect to the ECS instance.
3. Run the following command to generate the config file: cat /etc/sysconfig/network-scripts/ifcfg-[network interface name in the OS].
   Note

   • Pay attention to the relation between the network interface name in the OS and the MAC address.
   • Pay attention to the relation between the network interface name in the OS and the MAC address. The default route must be set to  DEFROUTE=no . Other editions must have the same configuration. Note that running the ifup command may change the active default route configuration after configuring the network interface.
   • Example:

     # cat /etc/sysconfig/network-scripts/ifcfg-eth1 
     DEVICE=eth1
     BOOTPROTO=dhcp
     ONBOOT=yes
     TYPE=Ethernet
     USERCTL=yes
     PEERDNS=no
     IPV6INIT = No
     PERSISTENT_DHCLIENT = Yes
     HWADDR=00:16:3e:12:e7:27
     DEFROUTE=noDefroute = No

4. To start the network interface, follow these steps:
   1. Run the ifup [network interface name in the OS]  command to start the dhclient process, and initiate a DHCP request. Example:

      # ifup eth1
      # ifup eth2

   2. After a response is received, run the ip a  a command to check the IP allocation on the network interfaces, which must match with the information displayed on the ECS console. Example:

      # 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 loInet 125.0.0.1/8 Scope host Lo
      valid_lft forever preferred_lft forever
      2: eth0: mtu 1500 qdisc pfifo_fast state UP qlen 10002: eth0: MTU 1500 qdisc glasstate up qlen 1000
      link/ether 00:16:3e:0e:16:21 brd ff:ff:ff:ff:ff:ff
      Inet 10.0.0.19/24 BRD glasscope Global Dynamic eth0
      valid_lft 31506157sec preferred_lft 31506157secValid_lft 31506157sec preferred_lft 31506157sec
      3: eth1: MTU 1500 qdisc glasstate up qlen 1000
      link/ether 00:16:3e:12:e7:27 brd ff:ff:ff:ff:ff:ff
      inet 10.0.0.20/24 brd 10.0.0.255 scope global dynamic eth1Inet 10.0.0.20/24 BRD glasscope Global Dynamic eth1
      Valid_lft 31525994sec preferred_lft 31525994sec
      4: eth2: MTU 1500 qdisc glasstate up qlen 1000
      Link/ether 00: 16: Rye: 12: 16: ec brd ff: FF: FF
      inet 10.0.0.21/24 brd 10.0.0.255 scope global dynamic eth2
      valid_lft 31526009sec preferred_lft 31526009sec

5. Set the metric for each network interface in the route table. In this example, set the metric parameters of eth1 and eth2 as follows.

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

   1. Run the following command to set the metric parameters.

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

   2. Run the route -n command to check whether the configuration is successful. Example:

      # 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
      0.5.0.0 10.0.0.253 ug ub1002 0 0 eth2
      10.0.0.0 0.5.0.0 255.25.25.0 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 0.5.0.0 255.25.25.0 u 0 0 0 eth2
      169.254.0.0 0.0.0 255.0.0 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 eth2169.254.0.0 0.0.0 255.0.0 U 1004 0 0 eth2

6. To build a route table, follow these steps:
   Note We recommend that you use the metric value as the route table name.
   1. Run the following command to build a route table.

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

   2. Run the following command to check whether the route table is built successfully.

      # ip route list table 1001
      default via 10.0.0.253 dev eth1
      # ip route list table 1002
      default via 10.0.0.253 dev eth2

7. Configure the policy routing.
   1. Run the following command to configure the policy routing.

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

   2. Run ip rule list to view the routing rules.

      # 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