The RIF in the IEEE 802.5 header is used by a source-route bridge to determine through which Token Ring network segments a frame must transit. Routing information that is on every interframe ring is made up of ring and bridge numbers, as well as other information. The RIF's progress through the network is recorded by the Route designator field. Assigned value that follows the ring number. This number does not have to be unique unless it is in parallel with another bridge connecting two rings.
Bridges add to the frame their bridge number and the ring number onto which the frame is forwarded.
Routes are alternating sequences of ring and bridge numbers that start and end with ring numbers. A single RIF can contain more than one Routing Designator field. Newer IBM bridge software programs combined with new LAN adapters support 13 hops. In contrast, RSRB passes the RIF through. This simplifies network management and troubleshooting.