IP hash and layer2

Hi, I'm not a network guy so, probably, it is a silly question. Please, be patient.

Using the IP HASH load balancing policy the vswitch will Choose an uplink based on a hash of the source and destination IP addresses of each packet.

That's clear but the vswitch is a layer2 device not a layer3 so how can ht see the IP address into the packet?

Thanks in advance

VMB