IPv4 Access Control Lists (ACLs)

Configuring Extended ACLs

Additional Options for TCP and UDP Traffic. An ACE designed to per­ mit or deny TCP or UDP traffic can optionally include port number criteria for either the source or destination, or both. Use of TCP criteria also allows the established option for controlling TCP connection traffic. (For a summary of the extended ACL syntax options, refer to table 9-7on page 9-53.)

Syntax: access-list < 100 - 199 > < deny permit > < tcp udp >

<SA > [comparison-operator < tcp/udp-src-port >]

<DA > [comparison-operator < tcp-dest-port >] [established]

<DA > [comparison-operator < udp-dest-port >]

This source-port and destination-port TCP/UDP criteria is iden­ tical to the criteria described for TCP/UDP use in named, extended ACLs, beginning on page 9-61.

Additional Options for ICMP Traffic. This option is useful where it is necessary to permit some types of ICMP traffic and deny other types, instead of simply permitting or denying all types of ICMP traffic. That is, an ACE designed to permit or deny ICMP traffic can optionally include an ICMP type and code value to permit or deny an individual type of ICMP packet while not addressing other ICMP traffic types in the same ACE. As an optional alterna­ tive, the ACE can include the name of an ICMP packet type. (For a summary of the extended ACL syntax options, refer to table 9-7on page 9-53.)

Syntax: access-list < 100 - 199 > < deny permit > icmp < SA > < DA > [[ icmp-type[ icmp-code]] [ icmp-type-name]]

The ICMP “type” and “code” criteria are identical to the criteria described for ICMP in named, extended ACLs, beginning on page 9-63.

Additional Option for IGMP. This option is useful where it is necessary to permit some types of IGMP traffic and deny other types, instead of simply permitting or denying all types of IGMP traffic. That is, an ACE designed to permit or deny IGMP traffic can optionally include an IGMP packet type to permit or deny an individual type of IGMP packet while not addressing other IGMP traffic types in the same ACE. (For a summary of the extended ACL syntax options, refer to table 9-7on page 9-53.)

9-71