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New Member

3750 span rate limitation

Does anybody know of a rate limitation on span traffic in the 3750? I have a customer that is using a 3750 to mirror call center traffic for monitoring and no matter what they do, they cannot seem to get more than 1850pps out of the span port. I have not been able to find any documentation that mentions a limitation so I am wondering if anybody else has run into this. Thanks!


Re: 3750 span rate limitation

The egress-SPAN data rate might degrade when fallback bridging or multicast routing is enabled. The amount of degradation depends on the processor loading. Typically, the switch can egress-SPAN at up to 40,000 packets per second (64-byte packets). As long as the total traffic being monitored is below this limit, there is no degradation. However, if the traffic being monitored exceeds the limit, only a portion of the source stream is spanned. When this occurs, this console message appears: Decreased egress SPAN rate.

In all cases, normal traffic is not affected; the degradation limits only how much of the original source stream can be egress-spanned. If fallback bridging and multicast routing are disabled, egress-SPAN is not degraded. There is no workaround. If possible, disable fallback bridging and multicast routing. If possible, use ingress-SPAN to observe the same traffic

New Member

Re: 3750 span rate limitation

I've the same question about SPAN rate limitation. I've a 3750 with ONE span session, one source and 10-12 destination ports. At the rate about 150 Mbps and more there is some degrade of spanned traffic.

It's not clear, is it switch or source problem.

So, since there is no such info on CCO about limitations, may be someone have exp in that question.

P.S. Switch is local standalone, no other proccess except SPAN.