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Catalyst 6500 Series Switch Software Configuration Guide—Release 8.7
OL-8978-04
Chapter 11 Configuring VLANs
Configuring Token Ring VLANs on the Switch
For source routing, the switch appears as a single bridge between the logical rings. The TrBRF can
function as a source-route bridge (SRB) or as a source-route transparent (SRT) bridge running either the
IBM or IEEE STP. If SRB is used, you can define the duplicate MAC addresses on the different logical
rings.
The Token Ring software runs an instance of STP for each TrBRF VLAN and each TrCRF VLAN. For
the TrCRF VLANs, STP removes loops in the logical ring. For the TrBRF VLANs, STP interacts with
the external bridges to remove the loops from the bridge topology, similar to STP operation on the
Ethernet VLANs.
Caution
Certain parent TrBRF STP and TrCRF bridge mode configurations can place the logical ports (the
connection between the TrBRF and the TrCRF) of the TrBRF in a blocked state. For more information,
see the
“Default VLAN Configuration” section on page 11-3
.
For source routing, the switch appears as a single bridge between the logical rings. The TrBRF can
function as an SRB or SRT bridge running either the IBM or IEEE STP. If SRB is used, the duplicate
MAC addresses can be defined on the different logical rings.
To accommodate the IBM System Network Architecture (SNA) traffic, you can use a combination of
SRT and SRB modes. In a mixed mode, the TrBRF considers some ports (logical ports that are connected
to TrCRFs) to operate in SRB mode while others operate in SRT mode.
Understanding How Token Ring TrCRF VLANs Work
The TrCRF VLANs define the port groups with the same logical ring number. You can configure two
TrCRF types in your network: undistributed and backup.
Typically, the TrCRFs are undistributed, which means that each TrCRF is limited to the ports on a single
switch. Multiple undistributed TrCRFs on the same or separate switches can be associated with a single
parent TrBRF (see
Figure 11-4
). The parent TrBRF acts as a multiport bridge, forwarding the traffic
between the undistributed TrCRFs.
Note
To pass data between the rings that are located on separate switches, you can associate the rings to the
same TrBRF and configure the TrBRF for SRB.
Figure 11-4
Undistributed TrCRFs
S6813
TrBRF 3
ISL
Switch A
Switch B
TrCRF
200
TrCRF
350
TrCRF
400