非常有意义的排错经历，关于option82请在本站中查找以前的文章，有专门的解释。 环境PC---cisco 2960 ---cisco 6506（dhcp server）这两天一直在测试，在cisco 2960开启 ip dhcp snooping 功能，下面的PC就获取不到地址在cisco 2960上抓包，发现dhcp_snooping工作正常，可以收到PC的dhcpdiscovery包，dhcp giaddr字段 0.0.0.0。...

http://www.cisco.com/warp/public/707/gre_ipsec_ospf.html ipsec over gre 跑组播 多播等...

2、GRE隧道：  IPSEC的问题：只支持单播流量，组播和广播流量是不会穿过数据SA的。GRE原理：将一个完整的组播和广播数据包封装在一个单播数据包（IPSEC）里，以处理如OSPF的组播或RIP的广播数据流，以完成对端的动态路由学习。cisco对GRE的应用，本质是：GRE处理广播、组播、非IP数据流，而IPSEC提供单播框架保护 ，以便在IP骨干网上传输。 拓扑图：192.168.1.0/24/R1/192.1.1.1——WAN—&m...

When NAT uses a route map to decide to create a translation entry, it will always create a "fully extended" translation entry. This translation entry will contain both the inside and outside (local and global) address entries and any TCP or...

ICMP类型 TYPE CODE Description Query Error 0 0 Echo Reply——回显应答（Ping应答） x   ...

Table Of ContentsConfiguring Unicast Reverse Path ForwardingIn This ChapterAbout Unicast Reverse Path ForwardingHow Unicast RPF WorksImplementing Unicast RPF RestrictionsRelated Features and TechnologiesPrerequisites to Configuring Unicast RPFUnicast...

在互联网的世界里，路由器是不可或缺的重要部件，没有它我们将没有办法和五彩斑斓的外部世界建立联系。因此，路由器的管理一直是网络管理员最重要的日常工作之一。         路由器是网络系统的主要设备，也是网络安全的前沿关口。如果路由器连自身的安全都没有保障，整个网络也就毫无安全可言。因此在网络安全管理上，必须对路由器进行合理规划、配置，采取必要的安全保护措施，避免因路由器自身的安全问题而给整个网络系统带来漏洞和风险。 下面是一些...

2811(config)#crypto isakmp client configuration group zbdcfs2811(config-isakmp-group)#?ISAKMP group policy config commands:  access-restrict    Restrict clients in this group to an interface  acl     ...

IP Cisco IOS IP Addressing Services Configuration Guide, Release 12.4 Cisco IOS IP Application Services Configuration Guide, Release 12.4 Cisco IOS IP Mobility Configuration Guide, Release 12.4 Cisco IOS IP Multicast Config...

IKE Aggressive Mode Behavior This section describes IKE aggressive mode behavior occurring when Cisco IOS software is used. IKE has two phases of key negotiation: phase 1 and phase 2. Phase 1 negotiates a security association (a key) b...

一个INSIDE口 多个OUTSIDE口的NAT配置 Feature HistoryRelease  Modification  12.2(4)T This feature was introduced. 12.2(4)T2 Support for the Cisco 7500 series routers was added. This document describes the NAT—Ability to ...

ContentsIntroductionPrerequisites      Requirements      Components Used      ConventionsBackground InformationAccess List Approach      Host 1 to Hos...

NAT and Same Security Level Interfaces NAT is not required between same security level interfaces even if you enable NAT control. You can optionally configure NAT if desired. However, if you configure dynamic NAT when NAT control is enabled, then NAT...

Order of NAT Commands Used to Match Real Addresses The security appliance matches real addresses to NAT commands in the following order: 1. NAT exemption (nat 0 access-list)—In order, until the first match. Identity NAT is not included in this ...

Bypassing NAT When NAT Control is Enabled If you enable NAT control, then inside hosts must match a NAT rule when accessing outside hosts. If you do not want to perform NAT for some hosts, then you can bypass NAT for those hosts (alternatively, you c...

Enable NAT−Traversal (#1 RA VPN Issue)NAT−Traversal or NAT−T allows VPN traffic to pass through NAT or PAT devices, such as a LinksysSOHO router. If NAT−T is not enabled, VPN Client users often appear to connect to the PIX or ...

Verify Crypto Map Sequence NumbersIf static and dynamic peers are configured on the same crypto map, the order of the crypto map entries is veryimportant. The sequence number of the dynamic crypto map entry must be higher than all of the other static...