Is this a nexus i wouldnt span a 10gb to a 1gb for obvious reasons of over subscription , even when you span 10gb source to 10gb dest you will prob get 5gb due to rate limit on nexus, you will most likely overload the port at that rate 10-1 ratio, you have to be careful with span , if you introduce too much for the switch to much you could crash the device or cause issues for your prod traffic as cpu is trying to process the monitored traffic
Configuring the Rate Limit for SPAN Traffic
By configuring a rate limit for SPAN traffic to 1Gbps across the entire monitor session, you can avoid impacting the monitored production traffic.
On Nexus 5000 series switches:
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When spanning more than 1Gbps to a 1 Gb SPAN destination interface, SPAN source traffic will not drop.
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When spanning more than 6 Gbps (but less than 10Gbps) to a 10Gb SPAN destination interface, the SPAN traffic is limited to 1Gbps even though the destination/sniffer is capable of 10Gbps.
