! enable RIPV2, but don't

  ! send updates

  ! check that packets are

  ! authentic

   interface eth0

   ip rip authentication string EZdozIt

  !

   router rip

   passive-interface eth0

  !

  The passive-interface clause is used because this host listens to routing updates, but does not send routing updates.   This is equivalent to the -q option mentioned earlier for the routed command.