Bảo trì hoạt động của Nghị định thư (MOP): MOP là được kích hoạt trên giao diện Ethernet và vô hiệu hóa trên tất cả các loại giao diện khác theo mặc định trong IOS. Để vô hiệu hóa MOP, sử dụng lau kích hoạt IOS lệnh trong chế độ cấu hình giao diện. Lệnh không lau cho phép phổ biến rộng rãi trong IOS. | IPsec VPN Services 381 Figure 7-4 Application of IPsec AH to IP Datagrams in Tunnel Mode and Transport Mode a IP Datagram - AH Transport Mode b IP Datagram - AH Tunnel Mode Original IP Datagram Original IP Header IP Payload Layer 2 Header New Tunnel IP Header AH Header Original 1 IP Header IP Payload Integrity Checked IPsec is designed per IETF standards for IP unicast-based traffic only. As such when there are requirements to apply IPsec to multicast applications non-IP traffic or routing protocols that use multicast or broadcast addressing then the additional use of a generic route encapsulation GRE tunneling is necessary. GRE provides the means for encapsulating many traffic types within unicast IP packets hence meeting the requirement for IPsec encapsulation. With IPsec and GRE working together support is available for multicast applications routing protocols such as Open Shortest Path First OSPF Routing Information Protocol RIP and Enhanced Interior Gateway Routing Protocol EIGRP or even the transport of non-IP traffic such as IPX or AppleTalk within an IPsec environment. A simple example configuration of an IPsec VPN using ESP encapsulation in tunnel mode is illustrated in Figure 7-5 with the corresponding configuration being given in Example 7-5. Figure 7-6 and corresponding configuration Example 7-6 show the same topology again for the comparable IPsec plus GRE architecture as a direct comparison. 382 Chapter 7 IP Services Plane Security Figure 7-5 IPsec VPN Deployment Using ESP Tunnel Mode Serial0 0 Serial0 0 Example 7-5 IPsec VPN Configuration Using ESP Tunnel Mode Router-A Configuration crypto isakmp policy 10 authentication pre-share crypto isakmp key cisco123 address crypto ipsec transform-set VPN-trans esp-3des esp-md5-hmac crypto map vpnmap local-address Serial0 0 crypto map vpnmap 10 ipsec-isakmp set peer set transform-set VPN-trans match address 101 interface Ethernet1 ip address interface Serial1 0 ip
