TN3270 Name Resolution Requires Fully Qualified Domain Names

ID: Q176280

The information in this article applies to:

Microsoft SNA Server, versions 3.0, 3.0 SP1, 3.0 SP2

SYMPTOMS

The TN3270 service included with SNA Server version 3.0 (and later) allows an administrator to restrict access to specific TN3270 clients by assigning either IP addresses or host names to LUA LUs/Pools assigned to the TN3270 service.

When you restrict access to TN3270 sessions using host names, TN3270 clients fail to connect to the TN3270 service if the host name used is the NETBIOS name (that is, computer name) of the client. The exact error that the client sees will depend on the TN3270 emulator being used.

The 3270 applet included with SNA Server 3.0 Service Pack 2 when configured for TN3270E Server Connection returns the following error when this problem occurs:

[TN3270-33]: ERROR - The server is unable to satisfy the session request.

A TN3270 internal trace returns the following message to the TN3270 client:

>10/31 14:00:50.491 (+ smidgen ) Event=TEV_DataToClient
Thread = 0x00000145 Session = 0x0009F6F0 Socket = 0x00000300
SUBNEG BEGIN TN3270E DEVICE-TYPE REJECT
Number of bytes = 9

CAUSE

If the TN3270 service is configured for Use Name Resolution, it requires the use of fully qualified domain names (FQDNs). The TN3270 service does not allow clients to connect to LUA LUs/Pools that are configured with client NETBIOS names.

Note: You must select the Use Name Resolution option under TN3270 Server properties when you restrict access via host names.

WORKAROUND

Specify the fully qualified domain names in the LUA LUs/Pools properties when restricting access by host name. A simple way of determining the FQDN for a client is to Ping the client. For example:


c:\> ping client1

  Pinging client1.dns.company.com [ip address] with 32 bytes of data:

  Reply from <ip address>: bytes=32 time<10ms TTL=128
  Reply from <ip address>: bytes=32 time<10ms TTL=128
  Reply from <ip address>: bytes=32 time<10ms TTL=128
  Reply from <ip address>: bytes=32 time<10ms TTL=128

In this case, the LUA LU/Pool should be configured with a name of client1.dns.company.com to allow a user on the CLIENT1 system to access this LU/Pool.

STATUS

The TN3270 service has been updated to correctly use both NETBIOS names and FQDNs for name resolution.

Microsoft has confirmed this to be a problem in SNA Server versions 3.0, 3.0 SP1, and 3.0 SP2.

This problem was corrected in the latest SNA Server version 3.0 U.S. Service Pack. For information on obtaining this Service Pack, query on the following word in the Microsoft Knowledge Base (without the spaces):

S E R V P A C K

MORE INFORMATION

The name resolution method used is determined by the Windows NT Server computer on which SNA Server is installed. There are currently four NetBIOS over TCP/IP name resolution methods: b-node, p-node, m-node, and h-node. For more information about these name resolution methods, please refer to the following Microsoft Knowledge Base article:

Q119493 NetBIOS over TCP/IP Name Resolution and WINS

To determine which name resolution method is being used by a Windows NT system, use the IPCONFIG utility from a command prompt as shown here:

c:\> ipconfig /all

The IPCONFIG /ALL command will return information similar to the following:

Windows NT IP Configuration


   Host Name . . . . . . . . . : server1.companyname.com
   DNS Servers . . . . . . . . : 123.23.234.123
                              123.23.235.124
   Node Type . . . . . . . . . : Mixed

   NetBIOS Scope ID. . . . . . :

   IP Routing Enabled. . . . . : No

   WINS Proxy Enabled. . . . . : No

   NetBIOS Resolution Uses DNS : No

Ethernet adapter El90x1:


   Description . . . . . . . . : 3Com 3C90x Ethernet Adapter

   Physical Address. . . . . . : 00-80-C7-55-55-C5

   DHCP Enabled. . . . . . . . : Yes

   IP Address. . . . . . . . . : 124.24.235.123

   Subnet Mask . . . . . . . . : 255.255.248.0

   Default Gateway . . . . . . : 124.24.235.1

   DHCP Server . . . . . . . . : 124.24.235.111

   Primary WINS Server . . . . : 123.23.234.125

   Secondary WINS Server . . . : 123.23.234.126

   Lease Obtained. . . . . . . : Tuesday, January 01, 1998 7:30:00 AM

   Lease Expires . . . . . . . : Saturday, November 05, 1998 7:30:00 AM

The name resolution method used for this sample system is Mixed (m-node) as shown by the Node Type parameter above.

Additional query words:

Keywords : snatn3270 kbfix3.00.sp3 snamanager
Version : WINDOWS:3.0,3.0 SP1,3.0 SP2
Platform : WINDOWS
Issue type : kbbug