3Com PathBuilder S200 Series Owner's Manual page 106

LLC2 Local Termination
Supported
Topologies
Improper LT
Configuration
102
Local Termination is supported only on Token Ring topologies configured for
Source Route Bridging. And there are two important guidelines to remember when
you are planning your Local Termination strategy:
• When you turn on Local Termination in your network, the MAC address/SAP
value you assign is always locally terminated.
• You must have a PathBuilder S200 series switch running Local Termination
positioned at both ends of your network to provide spoofing from one edge
point to another.
For example, Figure 51 shows a Token Ring network improperly configured for
Local Termination.
SNA
1
FEP
LLC2
Keepalives/Acks
Figure 51. Example of Improper LT Configuration
The cluster controller (CC) using non-PathBuilder S200 series switch bridge 3 in
Figure 51 is source route bridged to the FEP. The local PathBuilder S200 series
switch, bridge 1, at the FEP use location tries to locally terminate the session since
all frames bearing the MAC address of the FEP are to be spoofed. However, the non-
PathBuilder S200 series switch bridged cluster controller will never come up unless
Local Termination is disabled entirely. The cluster controller on PathBuilder S200
series switch bridge 2 will come up because it runs Local Termination. PathBuilder
S200 series switch bridge 2 is unable to spoof traffic unless it originates from its own
Token Ring. For spoofing to work, you must use PathBuilder S200 series switches
with Local Termination enabled at the network's edge points.
LLC2
Keepalives/Acks
2
CC
Non-3Com
3
Bridges
CC
Bridging