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ccna book in gujarati.When defining which packets need to be protected in an encryption ACL, it should be as explicit as possible. It is not recommended to use the keyword any to specify source or destination addresses. The statement permitanyany is strongly discouraged because it causes all outbound traffic to be protected and all protected traffic to be sent to the peer specified in the corresponding encrypted mapping entry, while all inbound packets lacking IPSec protection are silently discarded, including packets for routing protocols, NTP, echo, echo response, etc. If the keyword any must be used in a permit statement, this statement can be preceded by a series of deny statements to filter out traffic that should not be protected.Encrypted ACLs are associated with encrypted mappings, which are assigned to specific interfaces.238 Chapter 8 Implementing a Virtual Private Network8.4.5.3 Symmetric Encryption ACLsSymmetric Encryption ACLo must be configured for IPSec When a router receives a returned encrypted packet from an IPSec peer, it uses the same ACL and looks at the source and destination addresses in the ACL in reverse order to determine which inbound packets need to be decrypted. For traffic leaving one router, the ACL criteria is applied to the forward direction: for traffic entering the router, it is applied to the backward direction. In this way, the source of the directional ACL becomes the destination of the inbound ACL.For example, suppose that for Site 1, IPSec protects data traffic leaving interface R1S0/0/0 on Site 1 host on the 10.0.1.0/24 network that is routed to Site 2 host on the 10.0.2.0/24 network. For traffic originating from host 1 at site 1 on the 10.0.1.0/24 network and going to host 2 at site 2 on the 10.0.2.0/24 network, the ACL entries on R1 make the following determinations.Source = host on the 10.0.1.0/24 network Destination = host on the 10.0.2.0/24 network For inbound traffic from host at site 2 on the 10.0.2.0/24 network, going to host at site 1 on the 10.0.1.0/24 networkThe same ACL entry on R1 makes the following determinations: Source = host on network 10.0.2.0/24 Destination = host on network 10.0.1.0/24846 Task 5 - Applying Cryptographic Mapping8.4.6.1 Defining an encryption mapping