Title: Use of SRV records (_ldap, _kerberos, _kpasswd) (WAS: DNS vs. Hosts File)

Hi,

A few days ago we were talking about the different service records (_ldap, _kerberos and _kpasswd) and when these are used. Joe did a network trace and posted his findings. I was also curious and I also did network trace. Here are my findings. (I did not go through the traces thoroughly)

I did three network traces and used the following:

Configuration used:
* Windows 2003 SP0 installed and upgraded to SP1 -> DC/DNS
* Windows 2003 SP1 installed -> Client
* 1 AD domain
* Network monitor installed on both the client and the DC
* Network monitor used: Packetyzer 4.0.0

TRACES:
(1) Joining a client to an AD domain
--> _ldap SRV RR and _kerberos SRV RR used
--> NetBIOS also used to determine DCs. Don't understand this one!
--> Received "KRB5KRB_ERR_RESPONSE_TOO_BIG" several times.  Don't understand this one!
(2) Booting of a client and the logon of a user
--> _ldap  SRV RR used. Use of _kerberos SRV RR not detected, but kerberos authentication is used!
--> Received "KRB5KRB_ERR_RESPONSE_TOO_BIG" several times.  Don't understand this one!
(3) Password change of a user account
--> Received "KRB5KDC_ERR_S_PRINCIPAL_UNKNOWN".  The client used the SPN "cifs/172.16.1.11" instead of "cifs/w2k3dc01.w2k3domain.lan". Don't understand why.

As I know _kpasswd service record is for the Kerberos Password Change service, but I have not seen it being used in the trace.

For the specific findings see below.

Cheers,
#JORGE#
 
PS: If anyone is interested in also receiving the traces mail me offline

(1) findings:
Queries (FROM THE CLIENT TO THE DC)  --> 4x
          _ldap._tcp.dc._msdcs.W2K3DOMAIN.LAN: type SRV, class IN
               Name: _ldap._tcp.dc._msdcs.W2K3DOMAIN.LAN
               Type: SRV (Service location)
               Class: IN (0x0001)
Queries (FROM THE CLIENT TO THE DC)  --> 8x
          W2K3DOMAIN.LAN<1c>: type NB, class IN
               Name: W2K3DOMAIN.LAN<1c> (Domain Controllers)
               Type: NB
               Class: IN
Queries (FROM THE CLIENT TO THE DC)  --> 1x
          _kerberos._tcp.dc._msdcs.W2K3DOMAIN.LAN: type SRV, class IN
               Name: _kerberos._tcp.dc._msdcs.W2K3DOMAIN.LAN
               Type: SRV (Service location)
               Class: IN (0x0001)

Kerberos AS-REQ (User Datagram Protocol, Src Port: 1050 (1050), Dst Port: kerberos (88)) (FROM THE CLIENT TO THE DC)

Kerberos KRB-ERROR (User Datagram Protocol, Src Port: kerberos (88), Dst Port: 1050 (1050)) (FROM THE DC TO THE CLIENT)
     Pvno: 5
     MSG Type: KRB-ERROR (30)
     stime: 2005-05-07 20:20:00 (Z)
     susec: 665713
     error_code: KRB5KRB_ERR_RESPONSE_TOO_BIG (52)
     Realm: W2K3DOMAIN.LAN
     Server Name (Service and Instance): krbtgt/W2K3DOMAIN.LAN
          Name-type: Service and Instance (2)
          Name: krbtgt
          Name: W2K3DOMAIN.LAN

Kerberos TGS-REQ (User Datagram Protocol, Src Port: 1052 (1052), Dst Port: kerberos (88)) (FROM THE CLIENT TO THE DC)

Kerberos KRB-ERROR (User Datagram Protocol, Src Port: kerberos (88), Dst Port: 1052 (1052)) (FROM DC TO THE CLIENT)
     Pvno: 5
     MSG Type: KRB-ERROR (30)
     stime: 2005-05-07 20:20:01 (Z)
     susec: 962588
     error_code: KRB5KRB_ERR_RESPONSE_TOO_BIG (52)
     Realm: W2K3DOMAIN.LAN
     Server Name (Service and Instance): cifs/w2k3dc01.w2k3domain.lan
          Name-type: Service and Instance (2)
          Name: cifs
          Name: w2k3dc01.w2k3domain.lan

Kerberos TGS-REQ (User Datagram Protocol, Src Port: 1069 (1069), Dst Port: kerberos (88)) (FROM THE CLIENT TO THE DC

Kerberos KRB-ERROR (User Datagram Protocol, Src Port: kerberos (88), Dst Port: 1069 (1069)) (FROM THE DC TO THE CLIENT)
     Pvno: 5
     MSG Type: KRB-ERROR (30)
     stime: 2005-05-07 20:20:08 (Z)
     susec: 259463
     error_code: KRB5KRB_ERR_RESPONSE_TOO_BIG (52)
     Realm: W2K3DOMAIN.LAN
     Server Name (Service and Instance): ldap/w2k3dc01.w2k3domain.lan
          Name-type: Service and Instance (2)
          Name: ldap
          Name: w2k3dc01.w2k3domain.lan

(2) findings:
Queries (FROM THE CLIENT TO THE DC)  --> 3x
          W2K3DC01.W2K3DOMAIN.LAN: type A, class IN
               Name: W2K3DC01.W2K3DOMAIN.LAN
               Type: A (Host address)
               Class: IN (0x0001)

Queries  (FROM THE CLIENT TO THE DC)  --> 1x
          _ldap._tcp.Default-First-Site-Name._sites.W2K3DOMAIN.LAN: type SRV, class IN
               Name: _ldap._tcp.Default-First-Site-Name._sites.W2K3DOMAIN.LAN
               Type: SRV (Service location)
               Class: IN (0x0001)

Kerberos AS-REQ (User Datagram Protocol, Src Port: 1069 (1069), Dst Port: kerberos (88)) (FROM THE CLIENT TO THE DC)

Kerberos KRB-ERROR (User Datagram Protocol, Src Port: kerberos (88), Dst Port: 1069 (1069)) (FROM THE DC TO THE CLIENT)
     Pvno: 5
     MSG Type: KRB-ERROR (30)
     stime: 2005-05-07 20:27:19 (Z)
     susec: 90859
     error_code: KRB5KRB_ERR_RESPONSE_TOO_BIG (52)
     Realm: W2K3DOMAIN
     Server Name (Service and Instance): krbtgt/W2K3DOMAIN
          Name-type: Service and Instance (2)
          Name: krbtgt
          Name: W2K3DOMAIN

Kerberos TGS-REQ (User Datagram Protocol, Src Port: 1071 (1071), Dst Port: kerberos (88)) (FROM THE CLIENT TO THE DC)

Kerberos KRB-ERROR (User Datagram Protocol, Src Port: kerberos (88), Dst Port: 1071 (1071)) (FROM THE DC TO THE CLIENT)
     Pvno: 5
     MSG Type: KRB-ERROR (30)
     stime: 2005-05-07 20:27:19 (Z)
     susec: 106484
     error_code: KRB5KRB_ERR_RESPONSE_TOO_BIG (52)
     Realm: W2K3DOMAIN.LAN
     Server Name (Service and Host): host/w2k3sp1srv00.w2k3domain.lan
          Name-type: Service and Host (3)
          Name: host
          Name: w2k3sp1srv00.w2k3domain.lan

Kerberos TGS-REQ (User Datagram Protocol, Src Port: 1073 (1073), Dst Port: kerberos (88)) (FROM THE CLIENT TO THE DC)

Kerberos KRB-ERROR (User Datagram Protocol, Src Port: kerberos (88), Dst Port: 1073 (1073)) (FROM THE DC TO THE CLIENT)
     Pvno: 5
     MSG Type: KRB-ERROR (30)
     stime: 2005-05-07 20:27:20 (Z)
     susec: 75234
     error_code: KRB5KRB_ERR_RESPONSE_TOO_BIG (52)
     Realm: W2K3DOMAIN.LAN
     Server Name (Service and Instance): cifs/W2K3DC01.W2K3DOMAIN.LAN
          Name-type: Service and Instance (2)
          Name: cifs
          Name: W2K3DC01.W2K3DOMAIN.LAN

(3) findings
NO SRV RRs used here

Kerberos TGS-REQ (User Datagram Protocol, Src Port: 1085 (1085), Dst Port: kerberos (88)) (FROM THE CLIENT TO THE DC)

Kerberos KRB-ERROR (User Datagram Protocol, Src Port: kerberos (88), Dst Port: 1085 (1085)) (FROM THE DC TO THE CLIENT)
     Pvno: 5
     MSG Type: KRB-ERROR (30)
     stime: 2005-05-07 20:31:10 (Z)
     susec: 262734
     error_code: KRB5KDC_ERR_S_PRINCIPAL_UNKNOWN (7)
     Realm: W2K3DOMAIN.LAN
     Server Name (Service and Instance): cifs/172.16.1.11
          Name-type: Service and Instance (2)
          Name: cifs
          Name: 172.16.1.11

Met vriendelijke groet / Kind regards,

Jorge de Almeida Pinto
Infrastructure Consultant
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