MIT's name servers are all on their own network? Seriously?

  ;; AUTHORITY SECTION:
  mit.edu.              172800  IN      NS      bitsy.mit.edu.
  mit.edu.              172800  IN      NS      strawb.mit.edu.
  mit.edu.              172800  IN      NS      w20ns.mit.edu.
  
  ;; ADDITIONAL SECTION:
  bitsy.mit.edu.                172800  IN      A       18.72.0.3
  strawb.mit.edu.               172800  IN      A       18.71.0.151
  w20ns.mit.edu.                172800  IN      A       18.70.0.160