Kerberos not working correctly

We have spent weeks trying to get Kerberos and I am at a loss for why it is not working and figured I would turn to the forum to see if I can get the Issue Resolved.

We are running Vault v1.6.3+ent

We are wanting to use Kerberos authentication with keytabs.

My problem is my UPNDOMAIN is different from my Kerberos REALM.

I get the following error when trying to log in.

vault login -method=kerberos
username=user service=“HTTPS/”

Error authenticating: couldn’t log in: [Root cause: KRBMessage_Handling_Error] KRBMessage_Handling_Error: AS Exchange Error: AS_REP is not valid or client password/keytab incorrect < KRBMessage_Handling_Error: KDC did not respond appropriately to FAST negotiation

I set my ldap config up and it is working using LDAP auth. So I did my kerberos ldap the same way as it recommends.

if I set disable_fast_negotiation=true I get an error in my journalctl and also a debug message that shows the SPNEGO token was successful and it is pulling my valid credentials from my kdc server.
[INFO] auth.kerberos.auth_kerberos_0e58d037: user@CORP.DOMAIN.COM - SPNEGO authentication succeeded

[DEBUG] auth.kerberos.auth_kerberos_0e58d037: identity: &{username:user displayName:user realm:CORP.DOMAIN.COM cname:{NameType:1 NameString:[user]} keytab:0xc000fdfee0 password: attributes:map[gokrb5AttributeKeyADCredentials:{EffectiveName:user FullName:user UserID:212775 PrimaryGroupID:513 LogOnTime:{wall:918075300 ext:63753415503 loc:} LogOffTime:{wall:709551516 ext:68937867273 loc:} PasswordLastSet:{wall:648669600 ext:63750206191 loc:} GroupMembershipSIDs:
It pulls all of them

Kerberos config put in as
vault read /auth/kerberos/config
Key Value

service_account svc_account

LDAP config is
$ vault read /auth/kerberos/config/ldap
Key Value

anonymous_group_search false
binddn CN=svc_account,OU=Service Accounts,OU=Other,DC=corp,DC=domain,DC=com
case_sensitive_names false
certificate n/a
deny_null_bind true
discoverdn false
groupattr sAMAccountName
groupdn OU=Restricted Groups,DC=corp,DC=domain,DC=com
groupfilter (&(objectClass=group)(|(samaccountname=Valid_Group)(samaccountname=hash*)(samaccountname=vault*)))
insecure_tls false
starttls false
tls_max_version tls12
tls_min_version tls12
token_explicit_max_ttl 0s
token_max_ttl 0s
token_no_default_policy false
token_num_uses 0
token_period 0s
token_ttl 0s
token_type default
url ldap://
use_token_groups false
userattr cn
userdn CN=Users,DC=corp,DC=domain,DC=com

My kerberos realm is CORP.DOMAIN.COM

My user has a (Different and I know the instructions say to set the upndomain = kerberos realm (LDAP does not work when I do this)
user is in the Valid_Group so it should find it in the search as it works with normal ldap.

I can pull a service ticket from HTTPS/ doing $kvno HTTPS/
and it returns a kvno 2 which is what I have my keytab kvno number set to for my service account that the service account keytab is using and is put into the config.

Keytab name: FILE:vault.keytab
KVNO Timestamp Principal

2 04/02/2021 08:51:02 svc_account@CORP.DOMAIN.COM (aes256-cts-hmac-sha1-96)

user keytab kvno = 52 and that is in its keytab
slot KVNO Principal

1 1 user@CORP.DOMAIN.COM (aes256-cts-hmac-sha1-96)
2 1 user@CORP.DOMAIN.COM (aes256-cts-hmac-sha1-96)
3 52 user@CORP.DOMAIN.COM (aes256-cts-hmac-sha1-96)
4 0 user@CORP.DOMAIN.COM (aes256-cts-hmac-sha1-96)

I can do a klist -Ae and shoe that I can pull the tgt ticket and service tickets
klist -Ae
Ticket cache: KCM:8877:92714
Default principal: user@CORP.DOMAIN.COM

Valid starting Expires Service principal
04/07/2021 13:04:01 04/07/2021 23:03:45 HTTPS/
Etype (skey, tkt): aes256-cts-hmac-sha1-96, aes256-cts-hmac-sha1-96
04/07/2021 13:03:45 04/07/2021 23:03:45 krbtgt/CORP.DOMAIN.COM@CORP.DOMAIN.COM
renew until 04/14/2021 13:03:45, Etype (skey, tkt): aes256-cts-hmac-sha1-96, aes256-cts-hmac-sha1-96
04/07/2021 13:04:07 04/07/2021 23:03:45 HTTPS/
Etype (skey, tkt): aes256-cts-hmac-sha1-96, aes256-cts-hmac-sha1-96

Ticket cache: KCM:8877
Default principal: svc_account@CORP.DOMAIN.COM

Valid starting Expires Service principal
04/07/2021 13:03:22 04/07/2021 23:03:22 krbtgt/CORP.DOMAIN.COM@CORP.DOMAIN.COM
renew until 04/14/2021 13:03:22, Etype (skey, tkt): aes256-cts-hmac-sha1-96, aes256-cts-hmac-sha1-96

I will provide any addition configurations setup obfuscated with non-company identifiable info.

Any help will be greatly appreciated. Thanks