Users Guide

Applying Egress ACLs
Egress ACLs are supported on interfaces and affect the traffic leaving the system.
Configuring egress ACLs onto physical interfaces protects the system infrastructure from attack — malicious and incidental — by
explicitly allowing only authorized traffic. These system-wide ACLs eliminate the need to apply ACLs onto each interface and achieves the
same results. By localizing target traffic, it is a simpler implementation.
To restrict egress traffic, use an egress ACL. For example, when a direct operating system (DOS) attack traffic is isolated to a specific
interface, you can apply an egress ACL to block the flow from the exiting the box, thus protecting downstream devices.
To create an egress ACL, use the ip access-group command in EXEC Privilege mode. The example shows viewing the configuration,
applying rules to the newly created access group, and viewing the access list.
Example of Applying ACL Rules to Egress Traffic and Viewing ACL Configuration
To specify ingress, use the out keyword. Begin applying rules to the ACL with the ip access-list extended abcd command. To
view the access-list, use the show command.
Dell(conf)#interface gige 0/0
Dell(conf-if-gige0/0)#ip access-group abcd out
Dell(conf-if-gige0/0)#show config
!
gigethernet 0/0
no ip address
ip access-group abcd out
no shutdown
Dell(conf-if-gige0/0)#end
Dell#configure terminal
Dell(conf)#
ip access-list extended abcd
Dell(config-ext-nacl)#permit tcp any any
Dell(config-ext-nacl)#deny icmp any any
Dell(config-ext-nacl)#permit 1.1.1.2
Dell(config-ext-nacl)#end
Dell#
show ip accounting access-list
!
Extended Ingress IP access list abcd on gigethernet 0/0
seq 5 permit tcp any any
seq 10 deny icmp any any
seq 15 permit 1.1.1.2
Applying Layer 3 Egress ACLs on Control-Plane Traffic
By default, packets originated from the system are not filtered by egress ACLs.
For example, if you initiate a ping session from the system and apply an egress ACL to block this type of traffic on the interface, the ACL
does not affect that ping traffic. The Control Plane Egress Layer 3 ACL feature enhances IP reachability debugging by implementing
control-plane ACLs for CPU-generated and CPU-forwarded traffic. Using permit rules with the count option, you can track on a per-flow
basis whether CPU-generated and CPU-forwarded packets were transmitted successfully.
1 Apply Egress ACLs to IPv4 system traffic.
CONFIGURATION mode
ip control-plane [egress filter]
2 Apply Egress ACLs to IPv6 system traffic.
CONFIGURATION mode
ipv6 control-plane [egress filter]
3 Create a Layer 3 ACL using permit rules with the count option to describe the desired CPU traffic.
Access Control Lists (ACLs)
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