HP 6120G/XG HP ProCurve Series 6120 Blade Switches Access Security Guide - Page 350
How an ACE Uses a Mask To Screen Packets for Matches
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IPv4 Access Control Lists (ACLs) Traffic Management and Improved Network Performance ■ ACLs Operate On Ports and Static Trunk Interfaces: You can assign an ACL to any port and/or any statically configured trunk on the switch. ACLs do not operate with dynamic (LACP) trunks. ■ ACLs Screen Only the Traffic Entering the Switch on a Port or Static Trunk Interface: On a given interface, ACLs can screen inbound traffic at the point where it enters the switch. ACLs do not screen traffic routed between VLANs within the switch, between subnets in a multinetted VLAN, or at the interface where the traffic exits from the switch. (See figure 9-1 on page 9-11.) ■ Before Modifying an Applied ACL, You Must First Remove It from All Assigned Interfaces: An ACL cannot be changed while it is assigned to an interface. ■ Before Deleting an Applied ACL, You Must First Remove It from All Interfaces to Which It Is Assigned: An assigned ACL cannot be deleted. ■ Port and Static Trunk Interfaces: • Removing a port from an ACL-assigned trunk returns the port to its default settings. • To add a port to a trunk when an ACL is already assigned to the port, you must first remove the ACL assignment from the port. • Adding a new port to an ACL-assigned trunk automatically applies the ACL to the new port. How an ACE Uses a Mask To Screen Packets for Matches When the switch applies an ACL to inbound traffic on an interface, each ACE in the ACL uses an IP address and ACL mask to enforce a selection policy on the packets being screened. That is, the mask determines the range of IP addresses (SA only or SA/DA) that constitute a match between the policy and a packet being screened. 9-26
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