Cabletron Systems CSX400 Information on Source Routing, 4-58, Bridging, Source Route Configuration

Bridging

Figure 4-16. Source Route ConÞguration Window

Information on Source Routing

Source Routing is a bridging technique developed by IBM and the 802.5 standards committee in which a bridge routes frames based on the contents of their media access control frame header, rather than by maintaining a Þltering database to determine whether a packet should be forwarded or Þltered. Source Routing functions as follows:

¥An end point station transmits discovery (explorer) frames to a particular destination address in order to seek the best route through a bridged topology to that node. These frames are broadcast over the entire network.

In a network topology with parallel bridges, multiple paths may be available to the same destination. In this case, the explorer frame may be further deÞned as:

-All Routes Explorer, so that all possible routes to the destination are recorded, and multiple explorer frames can reach the same segment.

-Spanning Tree Explorer (also known as Single Route Broadcast), so that only one path is possible to a segment (i.e., through a designated bridge in a Spanning Tree topology), and only one explorer frame will be forwarded onto each segment. The Spanning Tree can be conÞgured either automatically (i.e., by algorithm) or manually.

4-58 Source Route Configuration