app\Http\Controllers\Auth\LoginController.php

<?php

namespace App\Http\Controllers\Auth;

use App\Http\Controllers\Controller;
use App\Providers\RouteServiceProvider;
use Illuminate\Foundation\Auth\AuthenticatesUsers;
use Illuminate\Http\Request;

class LoginController extends Controller {
    /*
      |--------------------------------------------------------------------------
      | Login Controller
      |--------------------------------------------------------------------------
      |
      | This controller handles authenticating users for the application and
      | redirecting them to your home screen. The controller uses a trait
      | to conveniently provide its functionality to your applications.
      |
     */

use AuthenticatesUsers;

    /**
     * Where to redirect users after login.
     *
     * @var string
     */
    protected $redirectTo = RouteServiceProvider::HOME;

    /**
     * Create a new controller instance.
     *
     * @return void
     */
    public function __construct() {
        $this->middleware('guest')->except('logout');
    }

    public function attemptLogin(Request $request) {
        $credentials = $request->only('email', 'password');
        \Auth::guard('admin')->attempt($credentials);
        if (\Auth::attempt($credentials))
        // Authentication passed...
            return redirect()->intended('dashboard');
    }

}

app\Models\AdminUser.php

<?php

namespace App\Models;

use App\Scopes\AdminUserScope;

class AdminUser extends User {

    protected $table = 'users';
    protected $guard = 'admin';

    protected static function booted() {
        static::addGlobalScope(new AdminUserScope);
    }

}

app\Providers\RouteServiceProvider.php

<?php

namespace App\Providers;

use Illuminate\Cache\RateLimiting\Limit;
use Illuminate\Foundation\Support\Providers\RouteServiceProvider as ServiceProvider;
use Illuminate\Http\Request;
use Illuminate\Support\Facades\RateLimiter;
use Illuminate\Support\Facades\Route;

class RouteServiceProvider extends ServiceProvider {

    /**
     * The path to the "home" route for your application.
     *
     * This is used by Laravel authentication to redirect users after login.
     *
     * @var string
     */
    public const HOME = '/home';

    /**
     * The controller namespace for the application.
     *
     * When present, controller route declarations will automatically be prefixed with this namespace.
     *
     * @var string|null
     */
    // protected $namespace = 'App\\Http\\Controllers';

    /**
     * Define your route model bindings, pattern filters, etc.
     *
     * @return void
     */
    public function boot() {
        $this->configureRateLimiting();

        $this->routes(function () {
            Route::prefix('api')
                    ->middleware('api')
                    ->namespace($this->namespace)
                    ->group(base_path('routes/api.php'));

            Route::middleware('web')
                    ->namespace($this->namespace)
                    ->group(base_path('routes/web.php'));

            Route::prefix('admin')
                    ->name('admin.')
                    ->namespace('Admin')
                    ->middleware(['web','auth:admin'])
                    ->group(base_path('routes/web_admin.php'));
        });
    }

    /**
     * Configure the rate limiters for the application.
     *
     * @return void
     */
    protected function configureRateLimiting() {
        RateLimiter::for('api', function (Request $request) {
            return Limit::perMinute(60)->by(optional($request->user())->id ?: $request->ip());
        });
    }

}

app\Scopes\AdminUserScope.php

<?php

namespace App\Scopes;

use Illuminate\Database\Eloquent\Builder;
use Illuminate\Database\Eloquent\Model;
use Illuminate\Database\Eloquent\Scope;

class AdminUserScope implements Scope {

    /**
     * Apply the scope to a given Eloquent query builder.
     *
     * @param  \Illuminate\Database\Eloquent\Builder  $builder
     * @param  \Illuminate\Database\Eloquent\Model  $model
     * @return void
     */
    public function apply(Builder $builder, Model $model) {
        $builder->where('is_admin', true);
    }

}

config\auth.php

<?php

return [

    /*
    |--------------------------------------------------------------------------
    | Authentication Defaults
    |--------------------------------------------------------------------------
    |
    | This option controls the default authentication "guard" and password
    | reset options for your application. You may change these defaults
    | as required, but they're a perfect start for most applications.
    |
    */

    'defaults' => [
        'guard' => 'web',
        'passwords' => 'users',
    ],

    /*
    |--------------------------------------------------------------------------
    | Authentication Guards
    |--------------------------------------------------------------------------
    |
    | Next, you may define every authentication guard for your application.
    | Of course, a great default configuration has been defined for you
    | here which uses session storage and the Eloquent user provider.
    |
    | All authentication drivers have a user provider. This defines how the
    | users are actually retrieved out of your database or other storage
    | mechanisms used by this application to persist your user's data.
    |
    | Supported: "session", "token"
    |
    */

    'guards' => [
        'web' => [
            'driver' => 'session',
            'provider' => 'users',
        ],
        'admin' => [
            'driver' => 'session',
            'provider' => 'admins',
        ],

        'api' => [
            'driver' => 'token',
            'provider' => 'users',
            'hash' => false,
        ],
    ],

    /*
    |--------------------------------------------------------------------------
    | User Providers
    |--------------------------------------------------------------------------
    |
    | All authentication drivers have a user provider. This defines how the
    | users are actually retrieved out of your database or other storage
    | mechanisms used by this application to persist your user's data.
    |
    | If you have multiple user tables or models you may configure multiple
    | sources which represent each model / table. These sources may then
    | be assigned to any extra authentication guards you have defined.
    |
    | Supported: "database", "eloquent"
    |
    */

    'providers' => [
        'users' => [
            'driver' => 'eloquent',
            'model' => App\Models\User::class,
        ],
        'admins' => [
            'driver' => 'eloquent',
            'model' => App\Models\AdminUser::class,
        ],

        // 'users' => [
        //     'driver' => 'database',
        //     'table' => 'users',
        // ],
    ],

    /*
    |--------------------------------------------------------------------------
    | Resetting Passwords
    |--------------------------------------------------------------------------
    |
    | You may specify multiple password reset configurations if you have more
    | than one user table or model in the application and you want to have
    | separate password reset settings based on the specific user types.
    |
    | The expire time is the number of minutes that the reset token should be
    | considered valid. This security feature keeps tokens short-lived so
    | they have less time to be guessed. You may change this as needed.
    |
    */

    'passwords' => [
        'users' => [
            'provider' => 'users',
            'table' => 'password_resets',
            'expire' => 60,
            'throttle' => 60,
        ],
    ],

    /*
    |--------------------------------------------------------------------------
    | Password Confirmation Timeout
    |--------------------------------------------------------------------------
    |
    | Here you may define the amount of seconds before a password confirmation
    | times out and the user is prompted to re-enter their password via the
    | confirmation screen. By default, the timeout lasts for three hours.
    |
    */

    'password_timeout' => 10800,

];