deny

博客详细介绍了英语单词deny的用法,包括表示‘说某事不真实’‘拒绝给予某人某物’‘不可否认’‘拒绝承认感受’‘节制自己’等含义,还给出了多种搭配及例句,同时列出了其同义词和相关英文解释。
//-----------重点-------------
2. NOT ALLOW   to refuse to allow someone to have or do something:
  [deny sb sth]
    She could deny her son nothing.

    I was denied the chance of going to university.     我得不到上大学的机会。
    She was angry at being denied the opportunity to see me. 因不准她见我, 她非常生气.

  [deny sth to sb]
    This is the only country in Europe to deny cancer screening to its citizens.

//-----------《LONGMAN Dictionary of Contemporary ENGLISH》-------------------------------
deny
v.denied, denying,denies [T]
1.SAY STH IS NOT TRUE to say that something is not true, or that you do not believe something;->denial:
  [deny(that)]
    I've never denied that there is a housing problem.
    I can't deny that her remarks hurt me.
  [deny doing something]
  [strongly/vehemently/strenuous etc deny sth]
  [deny the existence of]
  [deny a charge/allegation/chain]

2. NOT ALLOW   to refuse to allow someone to have or do something:
  [deny sb sth]
    She could deny her son nothing.

    I was denied the chance of going to university.     我得不到上大学的机会。
    She was angry at being denied the opportunity to see me. 因不准她见我, 她非常生气.

  [deny sth to sb]
    This is the only country in Europe to deny cancer screening to its citizens.

3.[there's no denying (that/sth)]  spoken
  used to say that it is very clear that something is true.

   There is no denying that this is an important event.
   
4.FEELINGS to refuse to admit that you are feeling something:
   Emotions can become destructive if they are suppressed and denied.

5.[deny yourself (sth)] to study not to have something that you would like, especially for moral or
   religious reasons:

   He denied himself all pleasures and luxuries.
   
   He denies himself nothing. 他对自己极为放纵.

//-----------DICT.CN---------------
1.    The accused man denies that he has ever met her.
    被告否认他曾经遇到过她。


2.    He has denied his country and his principles!
    他已经背弃了自己的国家和原则!


3.    I was denied the chance of going to university.
    我得不到上大学的机会。
4.    She was angry at being denied the opportunity to see me.
    因不准她见我, 她非常生气.


5.    He gave to his friends what he denied to his family.
    他宁可赠予朋友也不给家里人.


6.    He denies himself nothing.
    他对自己极为放纵.

//-----------------
动词deny:

1. declare untrue; contradict

2. refuse to accept or believe

3. refuse to grant, as of a petition or request

4. refuse to let have
同义词:refuse

5. deny oneself (something); restrain, especially from indulging in some pleasure
同义词:abnegate

6. deny formally (an allegation of fact by the opposing party) in a legal suit
同义词:traverse

7. refuse to recognize or acknowledge
//--------------------------------------------
<think>嗯,用户这次的问题很明确,是关于DHCP拒绝规则配置的。从"DHCP deny configuration usage"这个表述来看,用户应该是个网络管理员或者正在学习网络配置的技术人员,需要解决实际网络环境中的DHCP安全问题。 用户可能遇到了未经授权的DHCP服务器干扰网络的情况,这在企业网络中很常见。这类问题通常会导致IP地址冲突、网络中断等故障,所以用户才会专门询问"deny"这个阻止性命令的用法。 关于DHCP拒绝规则,主要涉及两个层面:一是阻止非法DHCP服务器响应客户端请求,二是限制合法DHCP服务器的配置范围。我注意到引用资料里提到Linux系统的底层网络协议实现,虽然不直接相关,但说明用户可能在使用Linux网络设备。 需要特别说明的是,不同厂商设备的配置命令差异很大。比如思科设备用"ip dhcp snooping trust",华为/H3C用"dhcp snooping enable",而Windows服务器根本不需要配置这个——因为它是基于端口信任模型的。用户没说明设备类型,所以我都得覆盖到。 用户应该需要知道具体操作步骤,所以给出示例配置很重要。但安全配置往往有坑,比如忘记开启snooping数据库会导致合法请求也被丢弃,这个陷阱必须提醒。另外用户可能不知道DHCP Snooping还能防ARP欺骗,这个增值功能值得强调。 考虑到用户后续可能遇到的问题,生成的问题要覆盖排错场景(如绑定表不生效)、扩展功能(结合DAI)以及替代方案(端口安全)。毕竟部署时这些都会连带出现。 最后决定用华为示例为主,因为引用资料里出现了华为命令格式。但必须标注其他厂商的差异,避免用户套用错误。那个"配置后DHCP请求被丢弃"的故障树特别实用,用户遇到问题时按这个排查能省不少时间。</think>理解DHCP拒绝规则(`dhcp deny`)对于网络安全管理至关重要,它主要用于**阻止非法DHCP服务器干扰网络**或**限制合法DHCP服务器的配置范围**。以下是详细解析和配置指导: --- ### 一、核心用途与原理 1. **防御Rogue DHCP攻击** 当非授权DHCP服务器(如恶意设备)响应客户端请求时,会导致IP地址冲突、网关劫持。通过`dhcp deny`规则可阻断其响应报文。 - **技术原理**:在交换机端口启用`DHCP Snooping`后,所有非信任端口的DHCP响应包(如DHCP Offer/Ack)会被丢弃,仅允许信任端口(如合法DHCP服务器所在端口)响应[^1]。 2. **限制地址池分配范围** 在合法DHCP服务器上,可通过`deny`指令排除特定地址: ```cisco ip dhcp pool MY_POOL network 192.168.1.0 255.255.255.0 deny 192.168.1.100 192.168.1.150 // 禁止分配此IP段 ``` --- ### 二、典型配置步骤(以华为交换机为例) ```cisco [Huawei] dhcp enable [Huawei] dhcp snooping enable // 全局启用DHCP监听 [Huawei-GigabitEthernet0/0/1] dhcp snooping trusted // 连接合法服务器的端口设为信任 [Huawei-GigabitEthernet0/0/2] dhcp snooping enable // 非信任端口默认拒绝DHCP响应包 ``` > ⚠️ **关键点**: > - 信任端口:允许转发DHCP响应 > - 非信任端口:丢弃DHCP响应(隐式`deny`规则生效)[^2] --- ### 三、跨厂商命令对比 | **功能** | 华为/华三命令 | 思科命令 | |------------------|----------------------------------|----------------------------------| | 启用DHCP监听 | `dhcp snooping enable` | `ip dhcp snooping` | | 设置信任端口 | `dhcp snooping trusted` | `ip dhcp snooping trust` | | 静态绑定表 | `user-bind static ip-mac` | `ip source binding` | --- ### 四、故障排查场景 当客户端无法获取IP时,检查: ```cisco [Huawei] display dhcp snooping packet statistics // 查看丢弃报文计数 [Huawei] display dhcp snooping binding // 验证绑定表是否生成 ``` 若非信任端口有大量`DHCP Offer`丢弃记录,表明存在非法DHCP服务器活动[^3]。 --- ### 五、扩展应用:结合DAI防御ARP欺骗 ```cisco [Huawei] arp anti-attack check user-bind enable // 启用ARP绑定检查 [Huawei] interface GigabitEthernet0/0/2 [Huawei-GigabitEthernet0/0/2] ip source check user-bind enable // 基于DHCP绑定表过滤ARP ``` > 📌 **最佳实践**:DHCP Snooping绑定表是DAI(动态ARP检测)和IP源防护的基础,形成完整的安全防护链[^1]。 ---
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