public function loginsub(Request $request){
        $credentials = $request->only('email', 'password');

        if(Auth::guard('sub_users')->attempt($credentials))
        {
            $user = Auth::guard('sub_users');
}

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

        'api' => [
            'driver' => 'passport',
            'provider' => 'users',
        ],

         'sub_users' => [
            'driver' => 'passport',
            'provider' => 'sub_users'
        ],
    ],

<?php
namespace App;
use LaravelPassportHasApiTokens;
use IlluminateNotificationsNotifiable;
use IlluminateFoundationAuthUser as Authenticatable;
class sub_users extends Authenticatable
{
  use HasApiTokens, Notifiable;
/**
* The attributes that are mass assignable.
*
* @var array
*/
protected $fillable = [
'name', 'email', 'password','type','login_ip',
];

/**
* The attributes that should be hidden for arrays.
*
* @var array
*/
protected $hidden = [
'password', 'remember_token',
];



}