Cisco 7609 User Manual

9-4
Cisco 7600 Series Router Cisco IOS Software Configuration Guide—12.1E
78-14064-04
Chapter 9 Configuring VLANs
Understanding How VLANs Work
Figure 9-1 Interconnected Token Ring TrBRF and TrCRF VLANs
For source routing, the Cisco 7600 series router appears as a single bridge between the logical rings. The
TrBRF can function as a source-route bridge (SRB) or a source-route transparent (SRT) bridge running
either the IBM or IEEE STP. If an SRB is used, you can define duplicate MAC addresses on different
logical rings.
The Token Ring software runs an instance of STP for each TrBRF VLAN and each TrCRF VLAN. For
TrCRF VLANs, STP removes loops in the logical ring. For TrBRF VLANs, STP interacts with external
bridges to remove loops from the bridge topology, similar to STP operation on 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 “VLAN Configuration Guidelines and Restrictions” section on page 9-8.
To accommodate IBM System Network Architecture (SNA) traffic, you can use a combination of SRT
and SRB modes. In a mixed mode, the TrBRF determines that some ports (logical ports connected to
TrCRFs) operate in SRB mode while other ports operate in SRT mode
Token Ring TrCRF VLANs
Token Ring Concentrator Relay Function (TrCRF) VLANs define port groups with the same logical ring
number. You can configure two types of TrCRFs in your network: undistributed and backup.
TrCRFs typically are undistributed, which means each TrCRF is limited to the ports on a single network
device. Multiple undistributed TrCRFs on the same or separate network devices can be associated with
a single parent TrBRF (see Figure 9-2). The parent TrBRF acts as a multiport bridge, forwarding traffic
between the undistributed TrCRFs.
Note To pass data between rings located on separate network devices, you can associate the rings to the same
TrBRF and configure the TrBRF for an SRB.
Token
Ring
001
Token
Ring
001
Token
Ring
002
Token
Ring
002
Token
Ring
011
Token
Ring
002
SRS SRS SRS
SRB or SRT
BRF
CRF
S6624

Cisco 7609 Specifications

General

Chassis Slots	9
Switch Fabric Capacity	720 Gbps
Power Supply Options	AC or DC
Product Type	Router
Form Factor	Rack-mountable
Supported Line Cards	Various Cisco 7600 Series line cards
Operating System	Cisco IOS
Management	CLI, SNMP
Forwarding Performance	400 Mpps
Maximum Power Consumption	4000 Watts
Redundancy	Yes
Interfaces/Ports	Various, depending on line cards installed