The packet-filtering process

Sequential comparison and action: When an ACL Access Control List. ACL is a common way of restricting certain types of traffic on a physical port. filters a packet, it sequentially compares each ACE Access Control Entry. ACE is an element in an ACL that includes access control information.’s filtering criteria to the corresponding data in the packet until it finds a match. The action indicated by the matching ACE Access Control Entry. ACE is an element in an ACL that includes access control information. (deny or permit) is then performed on the packet.

Figure 1  Example of sequential comparison

As shown above, the ACL Access Control List. ACL is a common way of restricting certain types of traffic on a physical port. tries to apply the first ACE Access Control Entry. ACE is an element in an ACL that includes access control information. in the list. If there is not a match, it tries the second ACE Access Control Entry. ACE is an element in an ACL that includes access control information., and so on. When a match is found, the ACL Access Control List. ACL is a common way of restricting certain types of traffic on a physical port. invokes the configured action for that entry (permit or drop the packet) and no further comparisons of the packet are made with the remaining ACEs in the list. This means that when an ACE Access Control Entry. ACE is an element in an ACL that includes access control information. whose criteria matches a packet is found, the action configured for that ACE Access Control Entry. ACE is an element in an ACL that includes access control information. is invoked, and any remaining ACEs in the ACL Access Control List. ACL is a common way of restricting certain types of traffic on a physical port. are ignored. Because of this sequential processing, successfully implementing an ACL Access Control List. ACL is a common way of restricting certain types of traffic on a physical port. depends in part on configuring ACEs in the correct order for the overall policy you want the ACL Access Control List. ACL is a common way of restricting certain types of traffic on a physical port. to enforce.

Implicit Deny: If a packet does not have a match with the criteria in any of the ACEs in the ACL Access Control List. ACL is a common way of restricting certain types of traffic on a physical port., the ACL Access Control List. ACL is a common way of restricting certain types of traffic on a physical port. denies (drops) the packet. If you need to override the implicit deny so that a packet that does not have a match will be permitted, then configure permit ipv6 any any as the last ACE Access Control Entry. ACE is an element in an ACL that includes access control information. in the ACL Access Control List. ACL is a common way of restricting certain types of traffic on a physical port.. This directs the ACL Access Control List. ACL is a common way of restricting certain types of traffic on a physical port. to permit (forward) packets that do not have a match with any earlier ACE Access Control Entry. ACE is an element in an ACL that includes access control information. listed in the ACL Access Control List. ACL is a common way of restricting certain types of traffic on a physical port., and prevents these packets from being filtered by the implicit deny ipv6 any.

Figure 2  Packet-filtering process in an ACL with N entries (ACEs)

For example, suppose you want to configure an ACL Access Control List. ACL is a common way of restricting certain types of traffic on a physical port. (with an ID of “Test-02”) to invoke these policies for IPv6 traffic entering the switch on VLAN Virtual Local Area Network. In computer networking, a single Layer 2 network may be partitioned to create multiple distinct broadcast domains, which are mutually isolated so that packets can only pass between them through one or more routers; such a domain is referred to as a Virtual Local Area Network, Virtual LAN, or VLAN. 100:

  1. Permit inbound IPv6 traffic from 2001:db8:0:fb::11:42.

  2. Deny only the inbound Telnet traffic from 2001:db8:0:fb::11:101.

  3. Permit inbound IPv6 traffic from 2001:db8:0:fb::11:101.

  4. Permit only inbound Telnet traffic from 2001:db8:0:fb::11:33.

  5. Deny any other inbound IPv6 traffic.

The following ACL Access Control List. ACL is a common way of restricting certain types of traffic on a physical port., when assigned to filter inbound traffic on VLAN Virtual Local Area Network. In computer networking, a single Layer 2 network may be partitioned to create multiple distinct broadcast domains, which are mutually isolated so that packets can only pass between them through one or more routers; such a domain is referred to as a Virtual Local Area Network, Virtual LAN, or VLAN. 100, supports the above case:

Figure 3  Example of how an ACL filters packets

To assign the above ACL Access Control List. ACL is a common way of restricting certain types of traffic on a physical port., you would use this command:

Switch(config)# vlan 100 ipv6 access–group Test–02 <vlan-in|vlan-out>

For example, suppose you want to configure an ACL Access Control List. ACL is a common way of restricting certain types of traffic on a physical port. on the switch (with an ID of “Test-02”) to invoke these policies for IPv6 traffic entering the switch on VLAN Virtual Local Area Network. In computer networking, a single Layer 2 network may be partitioned to create multiple distinct broadcast domains, which are mutually isolated so that packets can only pass between them through one or more routers; such a domain is referred to as a Virtual Local Area Network, Virtual LAN, or VLAN. 12:

The following ACL Access Control List. ACL is a common way of restricting certain types of traffic on a physical port. model, when assigned to inbound filtering on an interface, supports the above case:

It is important to remember that ACLs Access Control List. ACL is a common way of restricting certain types of traffic on a physical port. configurable on the switch include an implicit deny ipv6 any. That is, IPv6 packets that the ACL Access Control List. ACL is a common way of restricting certain types of traffic on a physical port. does not explicitly permit or deny will be implicitly denied, and therefore dropped instead of forwarded on the interface. If you want to preempt the implicit deny so that packets not explicitly denied by other ACEs in the ACL Access Control List. ACL is a common way of restricting certain types of traffic on a physical port. will be permitted, insert an explicit permit ipv6 any as the last ACE Access Control Entry. ACE is an element in an ACL that includes access control information. in the ACL Access Control List. ACL is a common way of restricting certain types of traffic on a physical port.. Doing so permits any packet not explicitly denied by earlier entries. (Note that this solution would not apply in the preceding example, where the intention is for the switch to forward only the explicitly permitted packets entering the switch on VLAN Virtual Local Area Network. In computer networking, a single Layer 2 network may be partitioned to create multiple distinct broadcast domains, which are mutually isolated so that packets can only pass between them through one or more routers; such a domain is referred to as a Virtual Local Area Network, Virtual LAN, or VLAN. 100.) (Note that this solution does not apply in the preceding example, where the intention is for the switch to forward only explicitly permitted packets routed on VLAN Virtual Local Area Network. In computer networking, a single Layer 2 network may be partitioned to create multiple distinct broadcast domains, which are mutually isolated so that packets can only pass between them through one or more routers; such a domain is referred to as a Virtual Local Area Network, Virtual LAN, or VLAN. 12.)