Cabletron Systems SSIM-A2-01, Installation And User Manual

Page: 13 / 88

4
SmartStack SSIM-A2-01/SSIM-A8-01 Installation
Rules to Remember
This section will help you understand the configuration restrictions for the SSIM-
Ax-01 ATM 155 Uplink Module. In brief, you must remember the following rules
when planning to install the uplink:
•
Only one VAP per uplink per VLAN
•
If you create parallel paths directly between switches, spanning tree must be
enabled
•
Configuration data follows the switch slot, not the uplink module
Frame Length Limit
When attaching to an ATM network with LANE, possible ATM frame sizes are
1516, 4544, 9234 and 18190 bytes.
The LANE frame size (ATM Forum: C3) is defined as including the two byte ATM
LANE overhead, but without the 4 bytes Token Ring CRC. This gives the
following relationship to the size of frames any “real” Token Ring station should
be using.
You must configure your Token Ring stations to a maximum frame size as above,
or to a lower value. Some protocols will negotiate frame sizes end-to-end, some
will only recognize frame size settings between end-stations, and yet others will
only use the frame size of the transmitting interface. If you configure the frame size
of all Token-Ring stations, all protocols will work.
TR-LANE Max
Data Frame Size
Token-Ring Max
Frame Size
1516 1514
4544 4542
Table 1. Maximum Frame Sizes