Old Cisco Systems LogoI was recently part of a discussion regarding whether or not lowering the load-interval on a Cisco router or switch interface from the default of 300 seconds had an impact on performance. Both sides made good points, but both were based on assumption and conjecture.

5 minute input rate 213000 bits/sec, 28 packets/sec
5 minute output rate 25000 bits/sec, 31 packets/sec

I have found that the default 300 seconds for load-interval is just not useful when doing any sort of troubleshooting. Five minutes is just too long a period to be averaging traffic over. By default, I add load-interval 30 to all my interface configurations.

There are those that claim that this will have a negative impact on performance. In all fairness, that was written in 2000 and might have been true at the time.

Cisco's 12.4 Interface Command Reference clearly indicates that "load data is gathered every five seconds." This means that the collection of load data is not affected by the load-interval command, but merely affects how load calculations are performed. Therefore, it is safe to change the load-interval to any allowed interval that is more suitable for your needs.

Be aware that load calculation affects more than just the output of show interfaces. This can also effect backup interfaces that are dialed when an interface reaches a particular load. If you use this or a similar feature, use load-interval with caution.