Named Ipv4 Acls; Acl Logging - Cisco Catalyst 2960-X Security Configuration Manual
Cisco ios release 15.0(2)ex
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Also See for Catalyst 2960-X:
- Command reference manual (135 pages) ,
- Hardware installation manual (34 pages) ,
- Getting started manual (25 pages)
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Standard and Extended IPv4 ACLs
• Transmission Control Protocol (tcp)
• User Datagram Protocol (udp)
Named IPv4 ACLs
You can identify IPv4 ACLs with an alphanumeric string (a name) rather than a number. You can use named
ACLs to configure more IPv4 access lists in a router than if you were to use numbered access lists. If you
identify your access list with a name rather than a number, the mode and command syntax are slightly different.
However, not all commands that use IP access lists accept a named access list.
The name you give to a standard or extended ACL can also be a number in the supported range of access
Note
list numbers. That is, the name of a standard IP ACL can be 1 to 99 and . The advantage of using named
ACLs instead of numbered lists is that you can delete individual entries from a named list.
Consider these guidelines before configuring named ACLs:
• Numbered ACLs are also available.
• A standard ACL and an extended ACL cannot have the same name.
• You can use standard or extended ACLs (named or numbered) in VLAN maps.
ACL Logging
The switch software can provide logging messages about packets permitted or denied by a standard IP access
list. That is, any packet that matches the ACL causes an informational logging message about the packet to
be sent to the console. The level of messages logged to the console is controlled by the logging console
commands controlling the syslog messages.
Because routing is done in hardware and logging is done in software, if a large number of packets match
Note
a permit or deny ACE containing a log keyword, the software might not be able to match the hardware
processing rate, and not all packets will be logged.
The first packet that triggers the ACL causes a logging message right away, and subsequent packets are
collected over 5-minute intervals before they appear or logged. The logging message includes the access list
number, whether the packet was permitted or denied, the source IP address of the packet, and the number of
packets from that source permitted or denied in the prior 5-minute interval.
The logging facility might drop some logging message packets if there are too many to be handled or if
Note
there is more than one logging message to be handled in 1 second. This behavior prevents the router from
crashing due to too many logging packets. Therefore, the logging facility should not be used as a billing
tool or an accurate source of the number of matches to an access list.
Catalyst 2960-X Switch Security Configuration Guide, Cisco IOS Release 15.0(2)EX
150
Configuring IPv4 ACLs
OL-29048-01
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