from NFS server, try
netstat -an | grep 2049
you should see something like
*.2049 *.* 0 0 49152 0 LISTEN
10.12.13.97.2049 10.12.13.90.914 49640 0 49640 0 ESTABLISHED
- first line saysthat nfsd (service number 2049) is listening on all interfaces
*.2049 LISTEN
- next line says there is a connection from distant host
10.12.13.90
- so connection goes on
10.12.13.X network
you will connect with network using netstat -in
Name Mtu Net/Dest Address Ipkts Ierrs Opkts Oerrs Collis Queue
lo0 8232 127.0.0.0 127.0.0.1 711988047 0 711988047 0 0 0
aggr1 1500 10.12.13.0 10.12.13.97 102780417 0 171623103 0 0 0
aggr2 1500 10.22.33.0 10.22.33.97 2944376600 0 2272441510 0 0 0
hence nfs is using aggr1.