ccna 3 certificate

ccna 3 certificate.In Extended ACLs, sequence numbers are used to indicate the order in which ACLs are processed. To add or delete an ACE using a sequence number, you must first enter the ACL sub-configuration mode of a named ACL or numbered ACL. Next, if you want to delete an entry, you can add the no parameter after the sequence number of the entry. To add an entry, specify a new sequence number that lies between the two ACEs, and that is where the new entry should appear.For compatibility with previous versions, if an entry without a sequence number is applied, the first entry will be assigned a sequence number whose value is 10, and the sequence number of subsequent entries is incremented by 10. If no sequence number is assigned to a new entry, the router will automatically place this entry at the bottom of the list and assign it an appropriate sequence number.4.1.1.9 How Cisco Routers Parse Standard ACLs4.1 Access Control Lists 85In a standard access list, CiscoIOS adds new entries by IP address in descending order, regardless of the sequence number. Therefore, the standardsequence number in an ACL is used as an identifier for a specific ACE, doing the deletion. Regardless of the order in which all entries are entered, they are placed in descending order of IP addresses, from special to general. In the standard access list ,CisocIOS uses an internal logic to configure the ACE and verify that ACLo host statements with specific IPv4 addresseswill be listed first, but not necessarily in the order in which they were entered. First, the IOS will place the host statements in a certain order, which is determined by a special hash function. The resulting result optimizes the lookup of host ACL entries. It is not ordered by IPv4 address. Range statements or network statements are listed after host statements, and network statements are listed in the order in which they are output.The following example shows the different entries of an existing standard ACL19.Router# show access-lists StandardIP accesslist 19 10permit 192.168.100.1 20permit 10.10.10.0,wildcard bits 0.0.0.25530permit 201.101.110.0,wildcard bits0.0.0.255 40deny any