service instance 20 ethernet
  description Internal site
  encapsulation dot1q 17
  rewrite ingress tag pop 1 symmetric
  xconnect 192.168.51.20 838969735 encapsulation mpls
   mtu 9202
 !
[download]

The above is exactly the configuration for each service instance. The extra indentation for the MTU is because the MTU is being applied to the configuration of the xconnect (xconnect being nested under service instance, mtu nested under xconnect). Hope that helps. edit: forgot a /