ccna 3 exam 2

ccna 3 exam 2.Any temporary self-reversing ACE created contains allow behavior to allow return traffic from this session to pass.4.1.4.5 Using Self-Reverse ACLsConfiguring a router to use a self-reversing ACL involves only the following steps. Step 1 Create an internal ACL so that it looks for new outbound sessions and creates a temporary self-reversing ACL. step 2 Create an external ACL so that it uses the self-reversing ACL to inspect return traffic. Step 3 Activate the named ACLo at the appropriate interface.The syntax for an internal ACL is as follows: Router(config)# ip access-list extended internal_ACL_nameRouter(config-ext-nacl)# permit protocol source-addr [source-mask] [operator operand] destination-addr [destination-mask] [operator operand] [established] reflect reflexive_ACL_name [timeout seconds]For example, the following commands are used to match internal users who use a Web browser and rely on DNS to access the Internet.R1(config)# ipaccess-list extended internalACL R1 (config-ext-nacl)# permit tcp any anyeq 80 reflect WEB-ONLY-REFLEXIVE-ACL R1 (config-ext-nacl) # permit udp anyany eq 53 reflect DNS-ONLY-REFLEXIVE-ACL timeout 10Cisco IOS creates two self-reversing ACEs to maintain session information for outbound Web connections (WEB-ONLY-REFLEXIVE-ACL) and DNS queries (DNS-ONLY-REFLEXIVE-ACL). Note that CiscoIOS sets a 10-second timeout for DNS queries.After an internal extended named ACL is created (which is created from the inverse ACE), these temporary entries are referenced when traffic returns to the network. This is achieved by creating a second extended named ACL. In this named ACL, the evaluate statement is used to reference the self-reversing ACE created by the internal ACLoRouter(config)# ip access-list extended external_ACL_name Router(config-ext-nacl)# evaluate reflexive_ACL_name