Last Updated on August 1, 2021 by Admin 1
An associate creates the following access list that she plans to apply to an interface on a router:access-list 100 permit ip any any log
What type of traffic could cause this ACL to place a heavy load on the CPU of the router, and what command could be used to reduce the impact of the ACL? (Choose two.)
- traffic that is CEF switched
- traffic that is process switched
- traffic that is fast switched
- ip access-list log-update threshold
- ip access-list logging interval
- logging rate limi
There are two contributors 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 the log messages. To reduce the impact of process switched traffic, the ip access-list logging interval command can be used. The interval is specified in milliseconds and represents how often a single packet is process switched. While the messages in the generated log entries may not be as comprehensive after this command is executed, the counter values that are generated by the show access-list and show ip-access list commands will still be accurate.
Packets that are not process switched (CEF switched and fast switched) will examined or accounted for in the logging, so they are not the source of the problem.
The ip access-list log-update threshold command is used to configure how often syslog messages are generated and sent after the initial packet match. While this would be a beneficial command to run, as it addresses the second source of CPU congestion that is the sending of the syslog messages, that was not listed as a traffic type option. Therefore, this would not be a solution to the issue presented by packet switched traffic.
The logging rate limit command also will reduce the impact of log generation and transmission on the CPU, but again, it does not address the issue presented by process switched traffic.
Configure and verify router security features