一、什么是 通配符 掩码 通配符 掩码是一个32位比特数，以点分十进制表示，告诉路由器数据包IP地址的哪些比特需要和access-list命令中给定的IP地址相匹配。 二、 通配符 掩码的作用 一条典型的ACL仅能指定一个要允许或拒绝IP的规则，如果要阻止多个地址或一
一、什么是通配符掩码
通配符掩码是一个32位比特数，以点分十进制表示，告诉路由器数据包IP地址的哪些比特需要和access-list命令中给定的IP地址相匹配。
二、通配符掩码的作用
一条典型的ACL仅能指定一个要允许或拒绝IP的规则，如果要阻止多个地址或一段范围的地址，那么如使用典型的ACL规则，则需要添加多条才能满足。这样导致工作量增多，易出错且ACL执行效率降低等不足。而通配符掩码就是解决批量范围的ACL应用。简单来说，通配符掩码定义了数据包地址的哪部分需要匹配ACL中已列出的地址，哪些部分不需要匹配。
对于只有0和255字节的通配符掩码，0字节表示需要匹配，255字节表示不需要匹配。
三、简单型通配符掩码
对于标准的IP地址，使用观察就可以确定数据包的哪些位会被ACL分析，具体参见下例：
允许单台主机的通配符掩码
172.16.33.134 0.0.0.0
允许某个/24网络所有主机的通配符掩码
192.168.0.0 0.0.0.255
允许某个/16网络所有主机的通配符掩码
172.16.0.0 0.0.255.255
允许某个/8网络所有主机的通配符掩码
10.0.0.0 0.255.255.255
四、复杂型通配符掩码求法
从上面可以看出通配符掩码能实现针对一段地址范围的过滤，如上面例子，也就是分别针对单个地址，C类地址，B类地址以及A类标准地址的网络地址进行精准匹配。那么除了标准的网络地址匹配外，对于有划分子网，或没有划分子网但希望实现对某段地址范围进行ACL控制，通配符掩码能不能实现呢？答案是可以的，参见下面的例子：
问题：有192.168.22.0/26的网络，如何实现通配符掩码进行ACL控制
方法一：根据块大小求得通配符掩码：块大小-1
已知/26,可知块大小=64，那么实现上述网络细分为四个子网：
192.168.22.0
192.168.22.64
192.168.22.128
192.168.22.192
(块大小-1)即是通配符掩码中不必进行精准匹配的部分，所以通配符掩码=0.0.0.63
方法二、根据子网掩码求通配符掩码：（255.255.255.255-子网掩码）
已知/26，所以子网掩码是：255.255.255.192
通配符掩码=255.255.255.255-子网掩码-0.0.0.63
四、通配符掩码与any/host关键字
某两个特殊的通配符掩码与any/host关键字含义相同，且IOS更倾向使用特殊关键字。
其中：host=0.0.0.0,表示所有的比特位都必须匹配
any=255.255.255.255,表示所有的比特位都不需要匹配
我儿子真帅!
How to Grant Permissions to New MySQL UsersMay 09, 2025 am 12:16 AMTograntpermissionstonewMySQLusers,followthesesteps:1)AccessMySQLasauserwithsufficientprivileges,2)CreateanewuserwiththeCREATEUSERcommand,3)UsetheGRANTcommandtospecifypermissionslikeSELECT,INSERT,UPDATE,orALLPRIVILEGESonspecificdatabasesortables,and4)
How to Add Users in MySQL: A Step-by-Step GuideMay 09, 2025 am 12:14 AMToaddusersinMySQLeffectivelyandsecurely,followthesesteps:1)UsetheCREATEUSERstatementtoaddanewuser,specifyingthehostandastrongpassword.2)GrantnecessaryprivilegesusingtheGRANTstatement,adheringtotheprincipleofleastprivilege.3)Implementsecuritymeasuresl
MySQL: Adding a new user with complex permissionsMay 09, 2025 am 12:09 AMToaddanewuserwithcomplexpermissionsinMySQL,followthesesteps:1)CreatetheuserwithCREATEUSER'newuser'@'localhost'IDENTIFIEDBY'password';.2)Grantreadaccesstoalltablesin'mydatabase'withGRANTSELECTONmydatabase.TO'newuser'@'localhost';.3)Grantwriteaccessto'
MySQL: String Data Types and CollationsMay 09, 2025 am 12:08 AMThe string data types in MySQL include CHAR, VARCHAR, BINARY, VARBINARY, BLOB, and TEXT. The collations determine the comparison and sorting of strings. 1.CHAR is suitable for fixed-length strings, VARCHAR is suitable for variable-length strings. 2.BINARY and VARBINARY are used for binary data, and BLOB and TEXT are used for large object data. 3. Sorting rules such as utf8mb4_unicode_ci ignores upper and lower case and is suitable for user names; utf8mb4_bin is case sensitive and is suitable for fields that require precise comparison.
MySQL: What length should I use for VARCHARs?May 09, 2025 am 12:06 AMThe best MySQLVARCHAR column length selection should be based on data analysis, consider future growth, evaluate performance impacts, and character set requirements. 1) Analyze the data to determine typical lengths; 2) Reserve future expansion space; 3) Pay attention to the impact of large lengths on performance; 4) Consider the impact of character sets on storage. Through these steps, the efficiency and scalability of the database can be optimized.
MySQL BLOB : are there any limits?May 08, 2025 am 12:22 AMMySQLBLOBshavelimits:TINYBLOB(255bytes),BLOB(65,535bytes),MEDIUMBLOB(16,777,215bytes),andLONGBLOB(4,294,967,295bytes).TouseBLOBseffectively:1)ConsiderperformanceimpactsandstorelargeBLOBsexternally;2)Managebackupsandreplicationcarefully;3)Usepathsinst
MySQL : What are the best tools to automate users creation?May 08, 2025 am 12:22 AMThe best tools and technologies for automating the creation of users in MySQL include: 1. MySQLWorkbench, suitable for small to medium-sized environments, easy to use but high resource consumption; 2. Ansible, suitable for multi-server environments, simple but steep learning curve; 3. Custom Python scripts, flexible but need to ensure script security; 4. Puppet and Chef, suitable for large-scale environments, complex but scalable. Scale, learning curve and integration needs should be considered when choosing.
MySQL: Can I search inside a blob?May 08, 2025 am 12:20 AMYes,youcansearchinsideaBLOBinMySQLusingspecifictechniques.1)ConverttheBLOBtoaUTF-8stringwithCONVERTfunctionandsearchusingLIKE.2)ForcompressedBLOBs,useUNCOMPRESSbeforeconversion.3)Considerperformanceimpactsanddataencoding.4)Forcomplexdata,externalproc
Hot AI Tools
Undresser.AI Undress
AI-powered app for creating realistic nude photos
AI Clothes Remover
Online AI tool for removing clothes from photos.
Undress AI Tool
Undress images for free
Clothoff.io
AI clothes remover
Video Face Swap
Swap faces in any video effortlessly with our completely free AI face swap tool!
Hot Article
Hot Tools
MantisBT
Mantis is an easy-to-deploy web-based defect tracking tool designed to aid in product defect tracking. It requires PHP, MySQL and a web server. Check out our demo and hosting services.
Atom editor mac version download
The most popular open source editor
MinGW - Minimalist GNU for Windows
This project is in the process of being migrated to osdn.net/projects/mingw, you can continue to follow us there. MinGW: A native Windows port of the GNU Compiler Collection (GCC), freely distributable import libraries and header files for building native Windows applications; includes extensions to the MSVC runtime to support C99 functionality. All MinGW software can run on 64-bit Windows platforms.
Dreamweaver Mac version
Visual web development tools
Zend Studio 13.0.1
Powerful PHP integrated development environment
