Elastic Compute Service:Overview

Term

Description

maximum number of entries

The maximum number of CIDR blocks in a prefix list or the maximum number of port ranges in a port list. For example, 10.0.0.0/8 and 172.16.0.0/12 are two CIDR blocks.

address family

The address family of entries in a prefix list. Prefix lists support the IPv4 or IPv6 address family. Entries in a prefix list must belong to the same address family.

CIDR block

The CIDR block is an addressing method used over the Internet, which is more efficient than traditional Classes A, B, and C addressing models in IP address allocation. A CIDR block uses the slash notation in the following format: <IP address>/<Length of the network prefix>.

• Example 1: Convert a CIDR block to an IP address range. For example, 10.0.0.0/8 can be converted into a 32-bit binary address of 00001010.00000000.00000000.00000000. /8 indicates that the left-most 8 bits in the address are the network prefix and the right-most 24 bits are the host address. The corresponding IP address range is from 00001010.00000000.00000000.00000000 to 00001010.11111111.11111111.11111111. The subnet mask of 10.0.0.0/8 is 255.0.0.0 in decimal notation, which indicates the IP addresses range from 10.0.0.0 to 10.255.255.255.

• Example 2: Convert an IP address range to a CIDR block.

  For example, in an IP address range from 192.168.0.0 to 192.168.31.255, the right-most two octets in the IP addresses are converted into 00000000.00000000 to 00011111.11111111 in the binary format. Accordingly, the left-most 19 bits (= 8 × 2 + 3) are fixed to the network prefix. This way, the IP address range can be converted to 192.168.0.0/19 in the CIDR block format.

port range

The port range in a port list entry, which is used to match the destination ports of traffic. Specify a port range in the format of <Start port number>/<End port number>, such as 8000/9000 or 22/22.

associated resource

A resource that references a prefix list or port list.

Item

Limit

Method to raise limits

The maximum number of prefix lists allowed for an Alibaba Cloud account per region

100

N/A

The maximum number of entries in a prefix list

200

N/A

The maximum number of resources that can be associated with a prefix list

1,000

N/A

The maximum number of port lists allowed for an Alibaba Cloud account per region

1,000

N/A

The maximum number of entries in a port list

2,000

N/A

The maximum number of resources that can be associated with a port list

1,000

N/A