Administrator Guide
Example of Permitting All Packets from a Specied Host
In this rst 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 ABC
Dell(conf-ext-nacl)#permit tcp host 10.1.1.1 any eq 24
Dell(conf-ext-nacl)#
deny ip any any fragment
Dell(conf-ext-nacl)
Example of Permitting Only First Fragments and Non-Fragmented Packets from a Specied Host
In the following example, the TCP packets that are rst fragments or non-fragmented from host 10.1.1.1 with TCP destination port equal to
24 are permitted. Additionally, all TCP non-rst fragments from host 10.1.1.1 are permitted. All other IP packets that are non-rst fragments
are denied.
Dell(conf)#ip access-list extended ABC
Dell(conf-ext-nacl)#permit tcp host 10.1.1.1 any eq 24
Dell(conf-ext-nacl)#permit tcp host 10.1.1.1 any fragment
Dell(conf-ext-nacl)#
deny ip any any fragment
Dell(conf-ext-nacl)
Example of Logging Denied Packets
To log all the packets denied and to override the implicit deny rule and the implicit permit rule for TCP/ UDP fragments, use a conguration
similar to the following.
Dell(conf)#ip access-list extended ABC
Dell(conf-ext-nacl)#permit tcp any any fragment
Dell(conf-ext-nacl)#permit udp any any fragment
Dell(conf-ext-nacl)#deny ip any any log
Dell(conf-ext-nacl)
When conguring ACLs with the fragments keyword, be aware of the following.
When an ACL lters packets, it looks at the fragment oset (FO) to determine whether it is a fragment.
• FO = 0 means it is either the rst fragment or the packet is a non-fragment.
• FO > 0 means it is dealing with the fragments of the original packet.
Congure a Standard IP ACL
To congure 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. To
set up extended ACLs, refer to Congure 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 Congure a drop or forward lter.
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 lters, keep in mind that you might need to insert a new lter. To prevent
reconguring multiple lters, assign sequence numbers in multiples of ve.
To view the rules of a particular ACL congured on a particular interface, use the show ip accounting access-list ACL-name
interface interface command in EXEC Privilege mode.
118
Access Control Lists (ACLs)