Viewing the Traffic from an ECS to the Internet Through an EIP

Solution Architecture

In this example, the ECS accesses the Internet through an EIP. O&M engineers need to view the traffic from the ECS to the Internet, so they create a flow log to collect the flow logs of the ECS network interface for analysis and fault locating.

Figure 1 Viewing the traffic from an ECS to the Internet

Constraints

For details about the restrictions on flow logs, see Constraints.

Resource Planning

In this example, the VPC, subnet, ECS, EIP, and VPC flow log must be in the same region but can be in different AZs.

The following resource details are only for your reference. You can modify them if needed.

Table 1 Resource planning

Resource	Quantity	Description
VPC and subnet	VPC: 1 Subnet: 1	VPC name: Set it as needed. In this example, VPC-A is used. VPC IPv4 CIDR block: Set it as needed. In this example, 192.168.0.0/16 is used. Subnet name: Set it as needed. In this example, Subnet-A01 is used. Subnet IPv4 CIDR block: Set it as needed. In this example, 192.168.0.0/24 is used.
ECS	1	Configure the ECS as follows: ECS Name: Set it as needed. In this example, ECS-01 is used. ECS flavor: In this example, flow logs of the network interface attached to ECS-01 are collected. Select the ECS flavor that supports flow logs. For details, see Constraints. Image: Set it as needed. In this example, public image Huawei Cloud EulerOS 2.0 Standard 64 bit is used. System Disk: In this example, a general-purpose SSD disk of 40 GiB is used. Data Disk: Set it as needed. In this example, no data disk is used. Network VPC: Select a VPC. In this example, VPC-A is used. Subnet: Select a subnet. In this example, Subnet-A01 is used. Security Group: In this example, the ECS is associated with security group Sg-X. Ensure that all rules in Table 2 are added. EIP: Select Auto assign and configure parameters such as EIP type and bandwidth as required. In this example, the EIP is 121.XX.XX.73. Private IP address: In this example, 192.168.0.110 is used.
VPC flow log	1	Name: Set it as needed. In this example, flowlog-A is used. Version: Select v1 in this example. Resource Type: Select NIC in this example. Resource: Set it as needed. In this example, select the network interface (IP address: 192.168.0.110) of ECS-01. Filter: Select All traffic in this example. Log Group: Select an existing or create a log group. The log group of this example is as follows: Log Group Name: Set it as needed. In this example, lts-group-A is used. Log Retention (Days): Set it as needed. In this example, 30 is used. Log Stream: Select an existing or create a log stream. The log stream of this example is as follows: Log Group Name: In this example, the log group name is lts-group-A. Log Stream Name: Set it as needed. In this example, lts-topic-A is used. Log Storage: You are advised to enable this function for log search and analysis. Log Retention (Days): Set it as needed. In this example, 30 is used.

Table 2 Security group Sg-X rules

Direction	Action	Type	Protocol & Port	Source/Destination	Description
Inbound	Allow	IPv4	TCP: 22	Source: 0.0.0.0/0	Allows remote logins to Linux ECSs over SSH port 22.
Inbound	Allow	IPv4	TCP: 3389	Source: 0.0.0.0/0	Allows remote logins to Windows ECSs over RDP port 3389.
Inbound	Allow	IPv4	All	Source: current security group (Sg-X)	Allows the ECSs in Sg-X to communicate with each other using IPv4 addresses.
Inbound	Allow	IPv6	All	Source: current security group (Sg-X)	Allows the ECSs in Sg-X to communicate with each other using IPv6 addresses.
Outbound	Allow	IPv4	All	Destination: 0.0.0.0/0	Allows ECSs in Sg-X to access the external networks using IPv4 addresses.
Outbound	Allow	IPv6	All	Destination: ::/0	Allows ECSs in Sg-X to access the external networks using IPv6 addresses.

If the source of an inbound rule is set to 0.0.0.0/0, all external IP addresses are allowed to remotely log in to your instances. Exposing port 22 or 3389 to the public network will leave your instances vulnerable to network risks. To address this issue, set the source to a trusted IP address, for example, the IP address of your local PC.

Procedure

Figure 2 shows the process for viewing the traffic from an ECS to the Internet.

Figure 2 Viewing the traffic from an ECS to the Internet

Step 1: Create Cloud Resources

1. Create a VPC with a subnet.

   For details, see Creating a VPC with a Subnet.

2. Create an ECS.

   For details, see Purchasing an ECS in Custom Config Mode.

Step 2: Create a VPC Flow Log

1. Create a log group and log stream on the LTS console.

   For details about how to create a log group, see Creating a Log Group.

   For details about how to create a log stream, see Creating a Log Stream.

2. Create a VPC flow log.

   For details, see Creating a VPC Flow Log.

Step 3: View the VPC Flow Log

The flow log collects the information about the traffic flowing through the network interface attached to ECS-01.

1. Remotely log in to ECS-01.

   For details, see How Do I Log In to My ECS?

2. Ping an IP address on the Internet from ECS-01 and collect logs:

   ping <IP-address-on-the-Internet>

   Example command:

   ping 117.XX.XX.122

   Information similar to the following is displayed. You can view the flow log records in about 10 minutes. Do not stop the ping command during flow log collection.

   [root@ecs-01 ~]# ping 117.XX.XX.122
   PING 117.XX.XX.122 (117.XX.XX.122) 56(84) bytes of data.
   64 bytes from 117.XX.XX.122: icmp_seq=1 ttl=49 time=26.5 ms
   64 bytes from 117.XX.XX.122: icmp_seq=2 ttl=49 time=26.3 ms
   64 bytes from 117.XX.XX.122: icmp_seq=3 ttl=49 time=26.2 ms
   ...

3. Wait for about 10 minutes and view the VPC flow log information by referring to Viewing a VPC Flow Log.

   You can enter the IP address (117.XX.XX.122) in the search box to quickly filter the logs of the communication between ECS-01 and the Internet.

   Figure 3 Viewing logs
   
   The flow log record is in the following format:

   <version> <project-id> <interface-id> <srcaddr> <dstaddr> <srcport> <dstport> <protocol> <packets> <bytes> <start> <end> <action> <log-status>

   • Example log: 1 1XX89aca74e640d9848a37dea0315d99 68dbbb2c-543a-4ff1-9615-38f74a29adaf 117.XX.XX.122 192.168.0.110 0 0 1 594 58212 1782877039 1782877639 ACCEPT OK
   • Log description: The VPC flow log version is 1. During the 10 minutes from 11:37:19 to 11:47:19 on July 1, 2026, the network interface (68dbbb2c-543a-4ff1-9615-38f74a29adaf) accepted the following packets. A total of 594 echo request (type=8,code=0) packets were sent from the source IP address (192.168.0.110) to the destination IP address (117.XX.XX.122) using ICMP (protocol=1). The total size of all packets was 58,212 bytes.

     For details about flow log data, see VPC Flow Log Data.

Step 4: Configure Cloud Structuring Parsing and Analyze Visualized Logs for the VPC Flow Log