How to configure the elastic network card after attaching it to the ECS instance

This article introduces how to configure the elastic network card after attaching it to the ECS instance, and focuses on the specific steps. The content of this article is very compact, and I hope you will study patiently.

Configure the elastic network adapter of the ECS instance

If your instance uses the following images, you do not need to manually configure the elastic network adapter (ENI):

CentOS 7.3 64-bit

CentOS 6.8 64-bit

Windows Server 2016 Data Center Edition 64-bit

Windows Server 2012 R2 Data Center Edition 64-bit

If your instance uses It is not one of these types of images, but you want to attach an elastic network card to the instance. You need to configure the elastic network card manually. This article takes the CentOS 7.2 64-bit system as an example to introduce how to configure the elastic network card attached to the Linux instance so that it can be recognized by your system.

Prerequisites

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

Operation steps

You should follow the following steps to configure the elastic network card:

Use the DescribeNetworkInterfaces interface or on the ECS console Get the primary private IP address, mask address, default route, and MAC address for each network card. The following are the steps on the ECS console:

Log in to the ECS management console.

Find the primary private IP address, mask address, default route, and MAC address for each network card. An example is as follows:

eth1 10.0.0.20/24 10.0.0.253 00:16:3e:12:e7:27
eth2 10.0.0.21/24 10.0.0.253 00:16:3e:12:16:ec

Remotely log in to the ECS instance.

Generate the network card configuration file: run cat /etc/sysconfig/network-scripts/ifcfg-[network card name].

Note

You need to pay attention to the corresponding relationship between the network card name and the MAC address.

The default route needs to be configured as DEFROUTE=no. Other distributions are similar to this. Be careful to avoid configuring the network card that causes ifup to change the currently active default route of the system.

The example is as follows:

# 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=no

Start the elastic network card:

Run the command ifup [network card name] to start the dhclient process and initiate a DHCP request. An example is as follows:

# ifup eth1
# ifup eth2

After the request returns, run the command ip a to check the network card IP allocation, and pay attention to whether it matches the network card information provided on the console. An example is as follows:

# 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:16:21 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:e7:27 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:ec 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

Plan the default routing metric value of each network card in the routing table as needed. In this example, assume that the metric values ​​of eth1 and eth2 are to be configured as follows.

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

Run the following command to plan the metric value.

# 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

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

# 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

Create a routing table:

Description

It is recommended that you keep the routing table name consistent with the planned metric value.

Run the following command to create a routing table.

# 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

Run the following command to check whether the routing table is created 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

Configure policy routing.

Run the following command to create policy routing.

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

Run the command ip rule list to view 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

At this point, you have completed the elastic network card configuration.

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