Information Technology Reference
In-Depth Information
Configuration Example of Source Route Bridging (Continued)
Example 4-7
!
interface tokenring 1
source-bridge 2 11 5
source-bridge spanning
!
interface tokenring 2
source-bridge 3 12 5
source-bridge spanning
The frame in this example from Token Ring 1 to Token Ring 2 is source routed as follows:
Ring 1 to Bridge 0xA to Ring 5 to Bridge 0xB to Ring 2. The RIF is 0830.001a.005b.0020.
NOTE
The CCIE candidate must master how the RIF is built. At the end of some of the following
sections, there is a paragraph on how the RIF looks.
SRT
SRT is specified in the IEEE 802.1d Appendix C standard. SRT bridges can forward traffic from
both transparent and source-route end nodes and form a common spanning tree with transparent
bridges. SRT bridges combine the implementations of transparent bridges and source-route
bridges and can distinguish between source-route and transparently bridged frames. SRT allows
transparent or source-route stations to communicate with other stations of the same type.
SRT bridges use a Routing Information Indicator (RII) bit to distinguish between SRB and
transparent bridge frames. The RII values are as follows:
•
0, means a RIF is present; use the SRB algorithm.
•
1, means a RIF is not present; the frame is transparently bridged.
SR/TLB
SR/TLB bridges provide bridging between Ethernet and Token Ring networks. The difference
between SR/TLB and SRT bridges is that SR/TLB bridges can forward frames between source-
route and transparently bridged networks. Considering the differences between these two
technologies, SR/TLB has many challenges to overcome so that transparent Ethernet networks
can communicate with SRB token ring networks and vice versa.
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