Contents
Introduction
The log and log-input Access Control Entry Options
Configuring a Log Update Threshold
Limiting ACL Logging–Induced Process Switching
Rate Limiting Syslog Messages
Configuration Example
Optimized ACL Logging
References
Directjet-Configuration.pdf'Does that MAC address on the Jetdirect match the MAC address in the DHCP table- Yes that is how I was able to match.' Is there a printer connected to this jetdirect? Currently Lexmark printer is connected to DirectJet using Parallel cable.' If you press the Test button ' - Yes it printed two pages. The log-input option enables logging of the ingress interface and source MAC address in addition to the packet's source and destination IP addresses and ports. The first packet logged via the log or log-input options will generate a syslog message. There are two scenarios in which subsequent log messages will not be sent immediately.
Logging-enabled access control lists (ACLs) provide insight into traffic as it traverses the network or is dropped by network devices. Unfortunately, ACL logging can be CPU intensive and can negatively affect other functions of the network device. There are two primary factors that contribute to the CPU load increase from ACL logging: process switching of packets that match log-enabled access control entries (ACEs) and the generation and transmission of log messages. Using the configuration commands detailed in this document, administrators can strike a balance between traffic visibility and the corresponding impact on device CPU load.
The log and log-input options apply to an individual ACE and cause packets that match the ACE to be logged. The log-input option enables logging of the ingress interface and source MAC address in addition to the packet's source and destination IP addresses and ports.
The first packet logged via the log or log-input options will generate a syslog message. There are two scenarios in which subsequent log messages will not be sent immediately. If the log-enabled ACE matches another packet with identical characteristics to the packet that generated a log message, the number of packets matched is incremented and then reported at five-minute intervals. Similarly, if any log-enabled ACE in any ACL on any interface matches a packet within one second of the initial log message, the match or matches are counted for five minutes and then reported. These periodic updates will contain the number of packets matched since the previous message.
The samples below illustrate the initial message and periodic updates sent by an IOS device with a default configuration using the log ACE option. In the following samples, the first log messages are representative of those created by an IPv4 ACL; the second log messages are representative of those created by an IPv6 ACL.
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