multiple public ip - Simple Application Server - Alibaba Cloud Documentation Center

A multiple-IP instance provides a dedicated public IP address for each website or application to improve network performance and security. These instances are suitable for scenarios such as game acceleration and account security enhancement on e-commerce, gaming, and short video platforms.. This topic describes the limits of multiple-IP instances, their default network and routing configurations, and how to modify these configurations.

Limits

Only Ubuntu 24.04, CentOS 7.6, Alibaba Cloud Linux 3, , and custom images created from these images support the multiple-IP instance family.
You cannot reset the system of a multiple-IP instance using a custom image.
The peak bandwidth in the instance plans for the multiple-IP instance family is 200 Mbps. This bandwidth is shared by multiple static public IP addresses:
- If the Static Public IP Address is 2 IPv4 Addresses, the peak bandwidth for each IP address is 100 Mbps.
- If the Static Public IP Address is 3 IPv4 Addresses, the peak bandwidth for each IP address is 67 Mbps.

Network configuration

Default network configuration

By default, a multiple-IP instance has two network interface cards (NICs): eth0 and eth1. The default network configuration file is shown in the following examples.

Ubuntu 24.04

The default network configuration file /etc/netplan/50-cloud-init.yaml is as follows:

Two IP addresses

network:
    ethernets:
        eth0:
            dhcp4: true
            dhcp4-overrides:
                route-metric: 100
            dhcp6: false
            match:
                macaddress: 00:16:3e:08:XX:XX    #MAC address of eth0
            set-name: eth0
        eth1:
            dhcp4: true
            dhcp4-overrides:
                route-metric: 200
            dhcp6: false
            match:
                macaddress: 00:16:3e:08:XX:XX    #MAC address of eth1
            set-name: eth1
    version: 2

Three IP addresses

network:
    ethernets:
        eth0:
            dhcp4: true
            dhcp6: false
            match:
                macaddress: 00:16:3e:09:XX:XX  #MAC address of eth0
            set-name: eth0
            dhcp4-overrides:
                route-metric: 100
        eth1:
            dhcp4: false
            dhcp4-overrides:
                route-metric: 200
            dhcp6: false
            match:
                macaddress: 00:16:3e:09:XX:XX   #MAC address of eth1
            set-name: eth1
            addresses:
                    - 172.26.32.200/18          #Private IP 1 on eth1
                    - 172.26.32.201/18          #Private IP 2 on eth1
            routes:
              - to: default
                via: 172.26.63.253    #Default gateway
    version: 2

CentOS 7.6, Alibaba Cloud Linux 3

Two IP addresses
- The default network configuration file /etc/sysconfig/network-scripts/ifcfg-eth0 is as follows:
```
DEVICE=eth0
BOOTPROTO=dhcp
ONBOOT=yes
```
- The default network configuration file /etc/sysconfig/network-scripts/ifcfg-eth1 is as follows:
```
DEVICE=eth1
BOOTPROTO=dhcp
ONBOOT=yes
TYPE=Ethernet
HWADDR=00:16:3e:09:XX:XX   #MAC address
DEFROUTE=no
```
Three IP addresses
- The default network configuration file /etc/sysconfig/network-scripts/ifcfg-eth0 is as follows:
```
DEVICE=eth0
BOOTPROTO=dhcp
ONBOOT=yes
```
- The default network configuration file /etc/sysconfig/network-scripts/ifcfg-eth1 is as follows:
```
DEVICE=eth1
BOOTPROTO=dhcp
ONBOOT=yes
TYPE=Ethernet
HWADDR=00:16:3e:09:XX:XX   #MAC address
DEFROUTE=no
```
- The default network configuration file /etc/sysconfig/network-scripts/ifcfg-eth1:1 is as follows:
```
DEVICE=eth1:1
TYPE=Ethernet
BOOTPROTO=static
ONBOOT=yes
IPADDR=172.26.32.206    #Private IP address
NETMASK=255.255.192.0   #Subnet mask
```

Modify the network configuration

If the default network configuration does not meet your business requirements, you can modify it. This example shows how to swap the private IP addresses of the eth1 and eth0 network interface cards for an Ubuntu 24.04 instance that has two IP addresses.

Remotely connect to the multiple-IP server. For more information, see Connect to a Linux server.
Execute the following command to view the subnet mask, the private IP addresses of the NICs, and the default gateway.
```
ifconfig
route -n
```
The output is similar to the following.
- NIC eth0
  - Private IP (inet): 172.26.32.207
  - Subnet mask (netmask): 255.255.192.0
  - Default gateway (Gateway): 172.26.63.253
- NIC eth1:
  - Private IP (inet): 172.26.32.208
  - Subnet mask (netmask): 255.255.192.0
  - Default gateway (Gateway): 172.26.63.253
Execute the following command to modify the default network configuration file.
```
sudo vim /etc/netplan/50-cloud-init.yaml
```

Press the i key to enter edit mode. Then, modify the network configuration.

This example swaps the private IP addresses of the eth1 and eth0 NICs.

network:
    ethernets:
        eth0:
            dhcp4: false    #Disable DHCP
            dhcp4-overrides:
                route-metric: 100
            dhcp6: false
            match:
                macaddress: 00:16:3e:08:XX:XX
            set-name: eth0
            addresses:
                    - 172.26.32.208/18          #Change the private IP on eth0 to the original private IP of eth1           
        eth1:
            dhcp4: false    #Disable DHCP
            dhcp4-overrides:
                route-metric: 200
            dhcp6: false
            match:
                macaddress: 00:16:3e:08:XX:XX
            set-name: eth1
            addresses:
                    - 172.26.32.207/18          #Change the private IP on eth1 to the original private IP of eth0
            routes:                             
              - to: default
                via: 172.26.63.253              #Configure the gateway on eth1
    version: 2

Press the Esc key, enter :wq, and press the Enter key to save the file and exit.
Execute the following command to apply the configuration.
```
sudo netplan apply
```
Execute the following command to verify that the configuration is applied.
```
ifconfig
```
The output is similar to the following. It indicates that the private IP addresses of the eth0 and eth1 NICs are modified.

Routing configuration

Multiple-IP instances are configured with default routing rules for the network interface cards. This ensures that traffic enters and exits through the correct public IP addresses.

Default routing configuration

For the IP address of eth0: Both inbound and outbound traffic pass through eth0.
For the IP address of eth1: Both inbound and outbound traffic pass through eth1.

Verify the default routing configuration

This example shows how to verify the configuration for an Ubuntu 24.04 instance that has two IP addresses:

On the instance card, click the instance ID to go to the Server Overview page. On this page, view the public IP address that corresponds to each private IP address.
Monitor Internet Control Message Protocol (ICMP) packets on the eth0 and eth1 NICs.
Monitor ICMP packets on eth0
1. Remotely connect to the multiple-IP server. For more information, see Connect to a Linux server.
2. Execute the following command to capture ICMP packets on the eth0 NIC.
```
tcpdump -i eth0 icmp
```
3. On a local computer with Internet access, execute the following command to send packets to the multiple-IP instance. Ping the public IP address that corresponds to the private IP address of eth0.
```
ping 39.XX.XX.103
```
4. In the command line window of the multiple-IP server, view the packet information for the eth0 NIC.
  The output is similar to the following. The packet enters through the eth0 NIC. After the request is received, the reply is also sent from the eth0 NIC. This indicates that both inbound and outbound traffic for the IP address of the eth0 NIC passes through eth0.
Monitor ICMP packets on eth1
1. Remotely connect to the multiple-IP server. For more information, see Connect to a Linux server.
2. Execute the following command to capture ICMP packets on the eth1 NIC.
```
tcpdump -i eth1 icmp
```
3. On a local computer with Internet access, execute the following command to send packets to the multiple-IP instance. Ping the public IP address that corresponds to the private IP address of eth1.
```
ping 47.XX.XX.135
```
4. In the command line window of the multiple-IP server, view the packet information.
  The output is similar to the following. The packet enters through the eth1 NIC. After the request is received, the reply is also sent from the eth1 NIC. This indicates that both inbound and outbound traffic for the IP address of the eth1 NIC passes through eth1.