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Chapter28 Configuring Network Security with ACLs
Understanding ACLs
Figure28-1 Using ACLs to Control Traffic to a Network
When you apply a port ACL to a trunk port, the ACL filters traffic on all VLANs present on the trunk
port.
With port ACLs, you can filter IP traffic by using IP access lists and non-IP traffic by using MAC
addresses. You can filter both IP and non-IP traff ic on the same Lay er 2 interf ace by a pplying both an IP
access list and a MAC access list to the interface.
Note You cannot apply more than one IP access list and one MAC access list to a Layer 2 interfac e. I f an I P
access list or MAC access list is already configur ed on a Lay er 2 inter face and you a pply a new IP access
list or MAC access list to the interface, the new ACL replaces the previously configured one.
Router ACLs
If the switch is running the metro IP access image, you can ap ply rou ter ACLs on sw itch virt u al
interfaces (SVIs), which are Layer 3 interfaces to VLANs; on physical Layer 3 interfaces; and on Laye r
3 EtherChannel interfaces. You apply router ACLs on interfaces for specific directions (inbou nd or
outbound). You can apply one router ACL in each direction on an interface.
One ACL can be used with multiple features for a given interface, and one feature can use multiple
ACLs. When a single router ACL is used by multiple features, it is examined multiple times.
The switch supports these access lists for IPv4 traffic:
•Standard IP access lists use source addresses for matching operations.
•Extended IP access lists use source and destination addresses and optional protocol type information
for matching operations.
Host A
Host B
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= ACL denying traffic from Host B
and permitting traffic from Host A
= Packet
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