Setting up my DLSw link with a Cisco 2811 router and the IBM 3174 controller

 ROUTER ARRIVED AND INSPECTED

The Cisco 2811 router arrived on Friday, a refurbished unit I bought on eBay. It seems that units like this come with a set of configurations and software that allow the user to work through the Cisco networking certifications. 

I, on the other hand, only want this to speak synchronous serial to the IBM 3174 and encapsulate SDLC from that link so that it can be routed over TCP/IP. The Hercules mainframe emulator has a 3705 communications controller emulation that implements DLSw with a TCP/IP socket on the PC running the mainframe software. 

I had separately purchased a serial interface module (WIC-2T) that I installed in a slot on the rear of the 2811 router. This has a compact 26 pin connector (two actually, since it hosts up to two serial links) into which I would plug a Cisco Smart Serial cable. 

The router appeared to be in good condition and it started up reasonably, booting from the CF card onboard and eventually going into its active and ready state. Since I hadn't hooked up to the console port, I had no way to check the condition beyond the evidence of the green color on the System indicator LED. 

I found that I needed to communicate to an RJ45 serial port at 9600 baud to use the console port, but didn't have the right kind of adapters on hand. I thus had to order an RJ45 to USB serial cable through Amazon for arrival on Saturday.

CONFIGURATION CABLE ARRIVED AND SETUP BEGINS

Plugging in the serial USB cable to my laptop and the other end to the router, I opened a terminal program on the laptop and powered on my router. The console demanded a username and password, but didn't accept the defaults for these routers. The seller did not provide any note with the credentials either.

There is a set of procedures to recover the password (actually to set a new one since the old is encrypted). The first didn't work but the second, involving removal of the configuration Compact Flash (CF) card and some commands reset the box, let me reinsert the CF to copy its configuration file while I had supervisor level access, then define the username and password I wanted. 

After that procedure and a reboot, I received a command prompt from the router, at which point I could begin to configure the DLSw for the SDLC line. I checked over the status and hardware elements of the box - it did see my two serial links from the module I added in, as well as the core hardware and adequate RAM. 

I had to configure the ethernet port as a private address range (e.g. starting with 192.168) with a fixed IP address that would allow me to connect to another fixed address on the PC running Hercules, the mainframe emulator.

I set up the configuration along the lines of this example from Matt Burk's DLSw page on 9track.net 

dlsw local-peer peer-id 192.168.0.95    ! Local interface for DLSw
                                        !
dlsw remote-peer 0 tcp 192.168.0.44     ! Remote system running Hercules
                                        !
interface FastEthernet0/0               ! Ethernet interface to Hercules
 ip address 192.168.0.95 255.255.255.0
                                        !
interface Serial0/0/0                   ! Serial interface to SDLC target
 encapsulation sdlc
 clock rate 64000                       ! 64 Kbit/s baud rate
 sdlc role primary                      ! Router is primary SDLC device
 sdlc vmac 4000.0999.0100               ! Virtual MAC address associated with
                                        !   the SDLC target. This is an
                                        !   arbitrary value but the last two
                                        !   digits should be 00
 sdlc address C1                        ! SDLC addess of SDLC target
                                        !   on the serial link
 sdlc xid C1 01700018                   ! XID to report to DLSw peers for
                                        !   the SDLC target
 sdlc partner 4000.1020.1000 C1         ! The MAC address of the remote SDLC
                                        !   partner (within Hercules).
                                        !   Currently this is unused so any
                                        !   value can be input however it
                                        !   may be used for selecting between
                                        !   NCPs in the future
 sdlc dlsw C1    

Essentially this is defining the serial interface number 0 as a link carrying SDLC from the 3174, which is wrapped in DLSw and routed over TCP/IP to the IP address and port of the Hercules instance on my laptop. Hercules, via its 3705 controller emulation and some code added by Matt, will strip off the DLSw and deliver the SDLC into the mainframe to MVS.  

WIRING THE CABLE BETWEEN THE ROUTER AND THE 3174

The cable I bought had Smart Serial plugs on both ends, but what I need is to connect Smart Serial to a female DB25 with the right signals on appropriate pins to communicate with my 3174. I do have documentation of the signals that must be routed to the various DB25 pins and the location on the Smart Serial cable for each of those. 

Thus, I cut the cable in half, giving me two cables with a Smart Serial plug on one side. I have several DB25 female connectors thus I will be able to create the cable I need fairly easily. Using a multimeter I determined the purpose of each wire in the cable and soldered them as needed to the DB25 connector.

CONFIGURING THE 3174 FOR SDLC

First I had to configure my 3174 controller for SDLC. It is currently configured for BSC protocol, but I can create a second Control diskette and using the Utility diskette, set it up as needed. I have no prior experience with administering VTAM/SDLC so I had to fumble around a bit to figure this out. Actually, I have no Cisco router administration experience either, doubling the fun or learning experience of this project.

Working through the planning guide and configuration worksheets, plus the Hercules side definition of the controller, I put together the options I believe are correct. After copying the Control diskette, I did a customize on the new Control image to implement the SDLC parameters.  Now I can choose the Control diskette to use the 3174 with either SDLC via the router or BSC through Mattis Lind's SyncDongle.