Concept Guide

Example of Permitting All Packets from a Specified Host
DellEMC(conf)#ip access-list extended ABC
DellEMC(conf-ext-nacl)#permit tcp host 10.1.1.1 any eq 24
DellEMC(conf-ext-nacl)#deny ip any any fragment
DellEMC(conf-ext-nacl)
In the following example, the TCP packets that are first fragments or non-fragmented from host 10.1.1.1 with TCP destination
port equal to 24 are permitted. Additionally, all TCP non-first fragments from host 10.1.1.1 are permitted. All other IP packets
that are non-first fragments are denied.
Example of Permitting Only First Fragments and Non-Fragmented Packets from a Specified Host
DellEMC(conf)#ip access-list extended ABC
DellEMC(conf-ext-nacl)#permit tcp host 10.1.1.1 any eq 24
DellEMC(conf-ext-nacl)#permit tcp host 10.1.1.1 any fragment
DellEMC(conf-ext-nacl)#deny ip any any fragment
DellEMC(conf-ext-nacl)
To log all the packets denied and to override the implicit deny rule and the implicit permit rule for TCP/ UDP fragments, use a
configuration similar to the following.
Example of Logging Denied Packets
DellEMC(conf)#ip access-list extended ABC
DellEMC(conf-ext-nacl)#permit tcp any any fragment
DellEMC(conf-ext-nacl)#permit udp any any fragment
DellEMC(conf-ext-nacl)#deny ip any any log
DellEMC(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 ACL
To 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 EMC Networking OS Command Line Interface
Reference Guide. To set 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 mode
ip access-list standard access-listname
2. Configure a drop or forward filter.
CONFIG-STD-NACL mode
seq 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 prevent
reconfiguring 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-name interface interface command in EXEC Privilege mode.
The following is an example of viewing the rules of a specific ACL on an interface.
DellEMC#show ip accounting access-list ToOspf interface gig 1/6
Standard IP access list ToOspf
seq 5 deny any
seq 10 deny 10.2.0.0 /16
seq 15 deny 10.3.0.0 /16
112
Access Control Lists (ACLs)