If I'm sending traffic from host A to B by a switch, will enabling a mirror/SPAN port increase the time it takes for my frames to get from A to B?
Nb: I'm not worried about the time it takes for the mirrored frame to reach my monitoring host. Just wondering if it will affect the network performance in a time-critical environment.
Has anyone tested this? (I would also welcome any links to a post/paper on this)
Best Answer
Typically, according to Cisco, "The impact on the high-speed switching fabric is negligible".
This of course depends on your switch, its fabric and the load on the switch itself. The port that is being sent the copied data could drop packets however, if it's oversubscribed too heavily. Personally, I've never experienced any sort of detriment by using mirroring or SPAN.
Here's a doc from Cisco directly about the subject on some of their cat lines: http://www.cisco.com/c/en/us/support/docs/switches/catalyst-6500-series-switches/10570-41.html#anc48