System information

Troubleshooting IBM 10-237
SDLC: Client Cannot Connect to Host over Router Running SDLLC
SDLC: Client Cannot Connect to Host over Router Running SDLLC
Symptom: Users cannot open connections to hosts on the other side of a router configured to support
SDLC Logical Link Control (SDLLC).
Table 10-11 outlines the problems that might cause this symptom and describes solutions to those
problems.
Table 10-11 SDLC: Client Cannot Connect to Host over Router Running SDLLC
Possible Problem Solution
SDLC timing problems
Step 1 Place a serial analyzer on the serial line attached to the source station and
monitor packets.
Step 2 If duplicate packets appear, check the router configuration using the show
running-config privileged exec command. Check to see whether the
local-ack keyword is present in the configuration.
Step 3 If the local-ack keyword is missing, add it to the router configuration for
SDLC interfaces.
Step 4 Local acknowledgment parameters can be adjusted in the router, the attached
device, or both. Adjust SDLC protocol parameters as appropriate. These
parameters are used to customize SDLC transport over various network
configurations. In particular, you might need to tune various LLC2 timer
values.
The following is a sample configuration using the local-ack command:
interface Serial 1
mtu 4400
no ip address
hold-queue 150 in
encapsulation stun
stun group 1
stun sdlc-role primary
sdlc line-speed 19200
sdlc n1 35200
sdlc address 04 echo
stun route address 4 tcp 156.28.11.1 local-ack clockrate
19200
For more information about configuring SDLC, refer to the Cisco IOS Bridging and
IBM Networking Configuration Guide and Bridging and IBM Networking Command
Reference.
Possible Problem Solution
SDLC physical or
data link-layer problem
Step 1 Use the show interface slot/port exec command to check the state of the
connection with the SDLC device.
Step 2 Look for USBUSY in the output, which indicates that the router is attempting to
establish an LLC connection. If the router is not USBUSY, make sure that the
physical and link layers are working properly. For more information, refer to the
section “SDLC: Router Cannot Communicate with SDLC Device” earlier in this
chapter.
Step 3 If the router is USBUSY, proceed to the next problem in this table.