Network FAQ

Basics

What CIDR?

CIDR, Classless Inter-Domain Routing, is a method of categorizing IP addresses for assigning IP addresses to users and routing IP packets efficiently over the Internet, and is more flexible than the traditional Class A, Class B, and Class C addressing models. For instance, the CIDR address block for IPv4 is represented as a four-part dotted decimal address followed by a slash and ending with a number in the range 0 to 32: A.B.C.D/N. The dotted decimal part is a 32-bit binary number divided into groups of four octets, just like the IPv4 address. The number after the slash is the prefix length, that is, from left to right, the number of bits that are treated as the segment number. For example, 192.168.0.0/19 represents the address 192.168.0.0 ~ 192.168.31.255, the first 19 bits of the value remains unchanged.

What is a netmask

The netmask is the value of the corresponding bit in the network address segment indicating the network segment is changed to 1, and the value of the corresponding bit of the host number is changed to 0, which is the corresponding netmask. For example, the mask of 192.168.0.0/19 is 255.255.224.0.

IP address problems

If you did not choose to create an elastic public IP when creating the cloud virtual machine, how can you get public access after creation?

If you do not choose to create an Elastic Public IP when creating a cloud virtual machine, you can create a separate Elastic Public IP to bind it to the corresponding cloud virtual machine. For detailed steps, please refer to Bind Elastic Public IP.

Can you change the IPv4 address after the cloud virtual machine is created?

If you need to change the public IPv4 address, you can unbind the original elastic public IP address, create a new elastic public IP and bind it to the cloud virtual machine. To change the intranet IPv4 address, Modify network configuration is used.

How do you get IP address information within the cloud virtual machine?

You can get the IP address by Query Instance Metadata to get the IP address. If you wish to obtain an intranet IP address, you may also do so by:

• Linux System Query by ifconfig command
• Windows system: Query with the ipconfig /all command

Is the public network bandwidth of cloud virtual machine shared or exclusive?

exclusive use

What is the in/out direction bandwidth

Inbound bandwidth: Bandwidth flowing into the cloud server ECS, e.g.: Cloud virtual machine to download external resources; FTP client to upload resources to cloud virtual machine. Outbound network bandwidth: The bandwidth flowing out of the cloud virtual machine, e.g.: The cloud virtual machine provides external access and the FTP client downloads internal resources of the cloud virtual machine.

What is the incoming and outgoing bandwidth limit for purchasing a public IP with 5Mbps bandwidth?

The bandwidth specified when purchasing a flexible public IP is the outgoing bandwidth. For elastic public IPs less than 100Mbps, the incoming bandwidth limit is unified at 100Mbps; for elastic public IPs more than 100Mbps, the incoming and outgoing bandwidths are unified.