将辅助私有IP地址分配给AWS EC2实例后无法访问RDS MySQL

Question

The instances are set up on a common VPC as follows:

• EC2 instance running Ubuntu Server 16.04 LTS on a public subnet
• RDS MySQL on a private subnet
• Both EC2 and RDS on common security group allowing inbound traffic on port 3306

The connection works fine when on the primary private IP address.

After assigning a secondary private IP address to the EC2 instance, I perform the following:

• Add the static IP to the /etc/network/interfaces.d/*.cfg file:

  Default file content:

  auto lo iface lo inet loopback

  auto eth0 iface eth0 inet dhcp

  Add static IP address:

  auto eth0:0 iface eth0:0 inet static address xx.xx.xx.xx

• Run sudo ifup eth0:0

After this, MySQL refuses the connection and returns this error message:

Cannot access the database: No route to host (DNS_OF_RDS)

The connection is re-established when I run sudo ifdown eth0:0 .

What am I missing out on?

Answer 1

我可以通过在文件/etc/network/interfaces.d/*.cfg末尾添加网络掩码地址（ netmask 255.255.xx.xx ）来使其工作。