Switch Security 6-17
• Extended IP ACL— Uses a source IP address, destination IP address and IP protocol type as basic
matching criteria. It can also include other parameters specific to a protocol type, like the source and
destination ports for TCP/UDP protocols.
• MAC Extended ACL— Uses source and destination MAC addresses and VLAN ID. It optionally, also uses
Ethertype information.
Port ACLs are also stateful and are not applied on every packet switched through the switch. Whenever a
packet is received inbound, it is examined against existing sessions to determine if it belongs to an
established session. ACLs are applied on the packet in the following manner:
1. If the packet matches an existing session, it is not matched against ACL rules and the session decides
where to send the packet.
2. If no existing sessions match the packet, it is matched against ACL rules to determine whether to accept
or reject it. If ACL rules accept the packet, a new session is created and all further packets belonging to
that session are allowed. If ACL rules reject the packet, no session is established.
A session is based on:
• Source IP address
• Destination IP address
• Source Port
• Destination Port
• ICMP identifier
• Incoming interface index
• IP Protocol
•Source MAC
• Destination MAC
•Ethertype
•VLAN-ID
• 802.1p bits
When a Port ACL is applied 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 ACL
• Non-IP traffic by using MAC addresses.
Both IP and non-IP traffic on the same Layer 2 interface can be filtered by applying both an IP ACL and a MAC
ACL to the interface.
You cannot apply more than one IP ACL and one MAC ACL to a Layer 2 interface. If an IP ACL or MAC ACL is
already configured on a Layer 2 interface and a new IP ACL or MAC ACL is applied to the interface, the new
ACL replaces the previously configured one.
6.4.1.3 Wireless LAN ACLs
Wireless LAN ACLs filter/mark packets based on the wireless LAN from which they arrive rather than
filtering packets on Layer 2 ports.
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