System information

Troubleshooting IBM
Book Title
10-240
Virtual Token Ring Addresses and SDLLC
The sdllc traddr command specifies a virtual Token Ring MAC address for an SDLC-attached
device (the device you are spoofing to look like a Token Ring device). The last two hexadecimal
digits of the virtual MAC address must be 00. The router then reserves any virtual ring address that
falls into the range xxxx.xxxx.xx00 to xxxx.xxxx.xxff for the SDLLC serial interface.
As a result, other IBM devices on an internetwork might have an LAA that falls in the same range.
This can cause problems if you are using local acknowledgment because routers examine only the
first 10 digits of the LAA address of a packet (not the last two, which are considered wildcards).
If the router sees an address that matches an assigned SDLLC LAA address, it automatically
forwards that packet to the SDLLC process. This can result in packets being incorrectly forwarded
to the SDLLC process and sessions never being established.
Note To avoid assigning conflicting addresses, be certain you know the LAA naming convention
used in the internetwork before assigning a virtual ring address for any SDLLC implementation.
SDLC: Sessions Fail over Router Running STUN
Symptom: SDLC sessions between two nodes fail when they are attempted over a router that is
running serial tunnel (STUN).
Note This section discusses troubleshooting procedures for STUN without local acknowledgment
(LACK). For STUN with LACK, the procedures are essentially the same, but remember that there
are two sessions, one from the primary to the router, and one from the secondary to the router.
Table 10-12 outlines the problems that might cause this symptom and describes solutions to those
problems.
Table 10-12 SDLC: Sessions Fail over Router Running STUN
1 FEP = front-end processor
2 XID = exchange of identification