Example of Permitting All Packets from a Specified HostIn this first example, TCP packets from host 10.1.1.1 with TCP destination port equal to 24 are permitted. All others are denied.Dell(conf)#ip access-list extended ABCDell(conf-ext-nacl)#permit tcp host 10.1.1.1 any eq 24Dell(conf-ext-nacl)#deny ip any any fragmentDell(conf-ext-nacl)Example of Permitting Only First Fragments and Non-Fragmented Packets from a Specified HostIn the following example, the TCP packets that are first fragments or non-fragmented from host 10.1.1.1 with TCP destination port equal to24 are permitted. Additionally, all TCP non-first fragments from host 10.1.1.1 are permitted. All other IP packets that are non-first fragmentsare denied.Dell(conf)#ip access-list extended ABCDell(conf-ext-nacl)#permit tcp host 10.1.1.1 any eq 24Dell(conf-ext-nacl)#permit tcp host 10.1.1.1 any fragmentDell(conf-ext-nacl)#deny ip any any fragmentDell(conf-ext-nacl)Example of Logging Denied PacketsTo log all the packets denied and to override the implicit deny rule and the implicit permit rule for TCP/ UDP fragments, use a configurationsimilar to the following.Dell(conf)#ip access-list extended ABCDell(conf-ext-nacl)#permit tcp any any fragmentDell(conf-ext-nacl)#permit udp any any fragmentDell(conf-ext-nacl)#deny ip any any logDell(conf-ext-nacl)When configuring ACLs with the fragments keyword, be aware of the following.When an ACL filters packets, it looks at the fragment offset (FO) to determine whether it is a fragment.• FO = 0 means it is either the first fragment or the packet is a non-fragment.• FO > 0 means it is dealing with the fragments of the original packet.Configure a Standard IP ACLTo configure an ACL, use commands in IP ACCESS LIST mode and INTERFACE mode.For a complete list of all the commands related to IP ACLs, refer to the Dell Networking OS Command Line Interface Reference Guide. Toset up extended ACLs, refer to Configure an Extended IP ACL.A standard IP ACL uses the source IP address as its match criterion.1 Enter IP ACCESS LIST mode by naming a standard IP access list.CONFIGURATION modeip access-list standard access-listname2 Configure a drop or forward filter.CONFIG-STD-NACL modeseq sequence-number {deny | permit} {source [mask] | any | host ip-address} [count [byte][dscp] [order] [monitor [session-id]] [fragments]NOTE: When assigning sequence numbers to filters, keep in mind that you might need to insert a new filter. To preventreconfiguring multiple filters, assign sequence numbers in multiples of five.To view the rules of a particular ACL configured on a particular interface, use the show ip accounting access-list ACL-nameinterface interface command in EXEC Privilege mode.Access Control Lists (ACLs) 121
