to connect as SYS over the network

  alter system set remote_login_passwordfile=exclusive scope=spfile;
  -- have to restart the db for this

setup a password file

  cd $ORACLE_HOME/dbs
  orapwd file=$ORACLE_HOME/dbs/orapw$ORACLE_SID password=oracle

connect using the password from the password file

   sqlplus "sys/oracle@REMOTE as sysdba"

where REMOTE is in your tnsnames.ora