Dell Unity: Users from trusted domain can't access the Unity NAS server (User Correctable)

spb:/cores/service/user# svc_cifssupport dan -pdcdump

dan : commands processed: 1
command(s) succeeded
output is complete

1660184568: SMB: 6: Dump DC for dom='CATEST' OrdNum=0
1660184568: SMB: 6: Domain=CATEST Next trusted domains update in 642 seconds
1660184568: SMB: 6:  oldestDC:DomCnt=0,2 Time=Thu Aug 11 02:17:18 2022

1660184568: SMB: 6:  Trusted domain info from DC='DC-1' (258 seconds ago)
1660184568: SMB: 6:   Trusted domain:trust.local [TRUST]
   GUID:00000000-0000-0000-0000-000000000000
1660184568: SMB: 6:    Flags=0x22 Ix=0 Type=0x2 Attr=0x8
1660184568: SMB: 6:    SID=S-1-5-15-dda732ea-ea90ce96-61bcbf65
1660184568: SMB: 6:    DC='-'
1660184568: SMB: 6:    Status Flags=0x0 DCStatus=0x547,0
>DC=DC0x0004e9bd18 DC-1[CATEST](10.10.100.100) ref=4 time(dns)=143 ms LastUpdt=Thu Aug 11 02:17:18 2022
    KrbAccount=DAN$@CATEST.LOCAL Status=OK lifetime:34788 seconds credUsage=0x1
     AccCred=0x0010089f08,0x001010c408 Buf=0x00063e3f58 L=2582 Flags=0x7
    Pid=0000 Tid=0001 Uid=500004000071 SMB=0x210
    Cnx=SUCCESS,DC request succeeded
    logon=SecureChannelOK 1 SecureChannel(s):
     [DAN] Fid=0x14000000a4 CallID=0x14 NLFlags=0x4107414d SessionKey:AES authV:[PRIVACY,sign:HMAC_SHA256,seal:AES128] Status=SUCCESS/SecureChannelOK
    Capa=0x0 MxBufSz=0xffff MawRwSz=0xffff Nego=0x0000000000,L=0 Chal=0x0000000000,L=0,W2kFlags=0x3f3fd
    refCount=4 newElectedDC=0x0000000000 forceInvalid=0
    Discovered from: DNS

Command succeeded

2022/08/10-02:34:41.193175    2     7F3E68B41700     sade:SMB: 6:[dan]  authenticate trust\administrator S=22 SamLogonInvalidReply
2022/08/10-02:34:41.193182    2     7F3E68B41700     sade:SMB: 6:[dan]  authLogon=SamLogonInvalidReply Es=0x0
Em=AUTHENTICATION_FIREWALL_FAILED U='administrator' D='trust'
2022/08/10-02:34:41.193194    5     7F3E68B41700     sade:SMB: 6:[dan]  2SMB470 SamLogon[0] DC=DC-1 'DC authn error' NTstatus=AUTHENTICATION_FIREWALL_FAILED LogonSt

/nas/bin/.server_config <nas server> -v "logsys set severity SMB=LOG_DBG3"

/nas/bin/.server_config <nas server> -v "logsys set severity SMB=LOG_PRINTF"

Selective authentication is a security setting that can be set on interforest trusts. It provides Active Directory administrators who manage a trusting forest more control over which groups of users in a trusted forest can access shared resources in a trusting forest. This increased control is especially important when administrators need to grant access to shared resources in their organization’s forest to a limited set of users located in another organization’s forest, because creating an external or forest trust provides a pathway for all authentication requests to travel between forests.

While this action by itself does not necessarily cause a threat to either forest, because all secured communications occur over the pathway, an external or forest trust exposes a larger surface to attack by any malicious user located in a trusted forest. Selective authentication helps to minimize this exposed area by enabling Active Directory administrators to grant a new authentication permission — to computer objects in the resource domain — for specific user accounts located in another organization’s forest.

- There are two solutions, customer can choose either of them based on their environment needs. 

1. Disable "selective authentication" in domain trust configuration. 

Enable selective authentication over an external trust: Domain and Forest Trusts | Microsoft Learn

2. Grant users in trusted domain with "Allowed to Authenticate" permission. 

Grant the Allowed to Authenticate permission on computers in the trusting domain or forest | Microsoft Learn