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General Explorer Filters for Token Ring Networks
This section provides examples of general explorer filters for token ring ports.
Dropping All Routes and Spanning Tree Explorers
Filter FLTR_A in Figure 6-6
drops all routes and spanning tree explorers from a
port.
Figure 6-6. Filter to Drop All Routes and Spanning Tree Explorers
FLTR_A sequence 1 is a MAC filter condition with an offset of 8 bytes, which is
the beginning of the source address field. This sequence checks if the source
routing indicator is turned on or off.
If the first byte of the source address is greater than or equal to 80, the frame
continues to sequence 2. If the first byte is less than 80, the frame skips sequence 2
and goes to the next filter group applied on the port. If no other filter groups are
applied to the port, the frame is forwarded as normal.
Sequence 2, also a MAC filter, offsets 14 bytes into the frame to check the
broadcast indicators in the routing control field. If the first byte is greater than or
equal to 80, the frame is dropped and does not continue to the next filter group
applied to the port. If the match condition fails, the frame ends the filtering
process for that port and is forwarded as normal.
Dropping Spanning Tree Explorers
Filter FLTR_B in Figure 6-7
drops spanning tree explorers from a port.
Figure 6-7. Filter to Drop Spanning Tree Explorers