cisco ccna 200-301 pdf free download

cisco ccna 200-301 pdf free download.The assumption here is that you want to limit the amount of traffic that can enter the network. The first statement states that as long as the destination address of the TCP session is located on network172.16.0.0/16 and the TCP data segment header is set with a specific flag bit (established ), indicating that it is returned traffic, it is allowed to pass. Don't forget that the keyword any is equivalent to 0.0.0.0255.255.255.255. Also, the keyword log causes a message to be displayed to the console every time it matches this statement. Since no TCP port is specified, all TCP connections match this statement.The second statement allows any source device to send DNS queries to the internal DNS server ( 172.16.1.1). Note that the wildcard mask 0.0.0.0 is not used here, and the keyword host is used in front of the IP address. again, each time this statement is matched, a message is written to the log.The third statement allows all Telnet traffic from network 172.17.0.0/16 to 172.16.1.2 to pass through. Don't forget that Telnet uses TCP. a message will also be written to the log each time this statement is matched. The fourth statement allows ping answers back to network 172.16.0.0/16 to pass. Note that only echo answers are allowed to pass, not echoes, which disables pinging of the corresponding interface. Each time this statement is matched, a message will also be written to the log. The fifth statement is redundant because traffic that does not match any of the previous permit statements is discarded. However, this statement needs to be configured if the discard is to be written to the log. At the end of the configuration, this ACL is applied to the inbound direction of interface ethemetO.Exam Points Please go back and review the previous Extended IPACL example to ensure that you understand how this ACL works.21.3.3 Named ACLsStarting with IOS 11.2, Cisco routers support numbered ACLs and named ACLs. one of the limitations of numbered ACLs is that the number of ACLs that can be created is limited. Initially, a maximum of 99 standard IPACLs and 100 extended IPACLs could be created; the other numbering was added several years ago. Starting with IOS 11.2, Cisco allows the use of names to identify ACLs. unlike numbered ACLs, in named ACLs, specific statements can be deleted without having to delete and recreate the ACL.Creating a Named ACL To create a named IPACL, use the following command. Router(config)# ip access-list (standard | extended} ACL_nameFirst, you must specify the type of ACL: standard or extended. Next, you must assign a name to the ACL that combines the ACL statements. The name must be unique among all named ACLs. After executing this command, you will enter the appropriate ACL sub-configuration mode, as follows.Router(config-std-acl)#