Configuring SNA Server through a 3174 gateway via 802.2

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SNA Server can access a host system through an IBM 3174 controller, where the 3174 is configured to support a downstream PU 2.0 computer through the 3174 gateway feature.

In this configuration, SNA Server is configured with an 802.2 connection with "remote end=host" (as a secondary PU 2.0 node), where the 3174 provides the gateway function to a mainframe system.

On the SNA Server computer, do the following:

1. Run SNA Server Setup and add an 802.2 link service.
2. Run SNA Server Admin and configure the 802.2 connection (associated with the 802.2 link service) from the Servers And Connections dialog box, using the following properties:
   • Remote End: Host System
   • Activation: (as desired by the administrator--default for 802.2 connections is On Server Startup)
   • Allowed Directions: Outgoing Calls must be selected (Incoming optional)
3. Zoom on the Setup button, and set the following additional parameters:
   • Remote Network Address: Enter the network card interface address of the 3174. This is set in Response 900 in the 3174 customization program.
     
     NOTE: If the 3174 is connecting to the host via X.25, Response 900 is no longer the destination for the SNA Servers on the network. The 3174 gateway now performs as a bridge between the SNA Servers on the network (Token Ring or Ethernet) and the X.25 hosts. Therefore, the destination for the SNA Servers is the ring address assigned to the X.25 host via Response 943 in the 3174 Customization program.
   • Local Node ID and Remote Node Name fields: not used--leave to defaults.
   • The Advanced settings can be left at the default settings.
4. Return to the main Servers And Connections dialog box. Focus on the 802.2 connection and create all required LUs off the connection (that is, 3270, LUA and/or dependent APPC LUs).
5. Optional: Configure pools of LUs through the LU Pools dialog box of SNA Server Admin.
6. Using the Users And Groups dialog box in SNA Server Admin, assign LUs and/or LU Pools to the appropriate users and groups.

On the IBM 3174 computer, do the following:

1. Using the 3174 configuration utility, configure downstream devices in Panel 940. Enter the SNA Server Token Ring network card (MAC) address in this panel. You can find the network card address of the SNA Server computer by entering "NET CONFIG WKSTA" from the command line of the Windows NT computer.
   
   When connecting over Ethernet, set the network card address in the 3174 Panel 940 to the bit-flipped version of the SNA Server local Ethernet address. The 3174 appears to bit-flip the incoming source address on the SNA Server XID message before matching against the addresses in the 940 screen. See below for instructions for determining the bit-flipped address.
   
   Most Windows NT adapters support overriding the network card address through the Windows NT network control panel. So, the SNA Server local network address could be set to match the address in Panel 940 on the 3174. The 3174 gateway feature recognizes the SNA Server computer by it's network card address only. If the address in Panel 940 does not match (either the actual address if Token Ring, or the bit-flipped address if Ethernet), the SNA Server connection will stay "Pending" and the following error will be reported in the Windows NT application event log:
   Event: 230 Remote station not responding to XID commands
   NOTE: If the 3174 is communicating to the host via X.25, Panel 940 is not used to configure downstream devices. 3174 Configuration Questions 942, 943 and 944 are used to help identify which downstream devices can communicate with the X.25 hosts.
   
   
2. Set the T value in panel 940 to Controller and not Workstation. If it is set to Workstation, the connection (PU) will become active but the LUs defined in SNA Server Admin will remain inactive. To allow "Workstation" to work properly, the SNA Server connection must be configured to send a Format 0 XID (configurable within SNA Server Admin connection's setup / advanced dialog).
3. Complete the 3174 configuration and reload it according to 3174 procedures.

Determining a bit-flipped Ethernet address:

1. Separate the 12-digit hexadecimal address into a set of two digits. For example:

   40000A123456       ->   40 00 0A 12 34 56

2. Reverse the positions of the characters in each of the two-digit sets. For example:

   40 00 0A 12 34 56  ->   04 00 A0 21 43 65

3. Use the table below to bit-reverse each digit. For example:

   04 00 A0 21 43 65  ->   02 00 50 48 2C 6A

      Conversion Table
      ----------------
   
      Original  Converted
      Bit       Bit
      --------  ---------
      0          0
      1          8
      2          4
      3          C
      4          2
      5          A
      6          6
      7          E
      8          1
      9          9
      A          5
      B          D
      C          3
      D          B
      E          7
      F          F

4. After bit-reversing each digit, combine the six pairs into a 12-digit hexadecimal address. For example:

   020050482C6A