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.Xnetwork
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.