Yes but filter should be used if you are monitoring for example a trunk so it will monitor only the vlans configured passing through it, also please check these links:
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so the source e2/1-2 must be trunk? can the destination port in the other slot, for example ge3/0/1 rather than ge2/0/5(not e2/5, we are using nexus)? thanks
if you have a interface trunk and many vlans are passing through it but you want to monitor only certain vlans, you should include on the span session the filter command.
I configured below span session in Nexus 1000v:
monitor session 2
source interface e2/1-2
source vlan 3,6-8 tx
filter vlan 3-5,7
destination int E2/5
is the above configuration correct?
Apart from Julio message , have a look on the below link for pre-requisite for SPAN.
Hope it Helps..