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A-10 APPENDIX A: PACKET FILTER OPCODES, EXAMPLES, AND SYNTAX ERRORS
Type Filter This filter operates on the type field of a frame. It allows packets to be
forwarded that are IP frames. To customize this filter to another type value,
change the literal value loaded in the
pushLiteral.w instruction.
name “Forward IP frames”
pushField.w 12 # Get type field
pushLiteral.w 0x0800 # Load IP type value
eq # Check for match
Ethernet Type IPX
and Multicast Filter
This filter rejects frames that have either a Novell IPX Ethernet type field
(8134 hex) or a multicast destination address.
name “Type > 900 or Multicast”
pushField.w 12 # Get type field
pushLiteral.w 0x900 # Push type value to test
# against
gt # Is type field > 900 (hex)?
reject # If yes: reject frame (done)
pushLiteral.b 0x01 # Multicast bit is low-order bit
pushField.b 0 # Get 1st byte of destination
and # Isolate multicast bit
not # Top of stack 1 to accept,
# 0 to reject
Multiple
Destination
Address Filter
This filter operates on the destination address field of a frame. It allows
packets to be forwarded that are destined for one of four different stations.
To customize this filter to other destination stations, change the literal
values.
name “Forward to four stations”
pushField.a 0 # Get destination address
pushTop # Make 3 copies of address
pushTop #
pushTop #
pushLiteral.a 0x367002010203# Load allowed destination
# address
eq # Check for match
accept # Forward if valid address
pushLiteral.a 0x468462236526# Load allowed destination
# address
eq # Check for match
accept # Forward if valid address
pushLiteral.a 0x347872927352# Load allowed destination
# address
eq # Check for match
accept # Forward if valid address
pushLiteral.a 0x080239572897# Load allowed destination
# address
eq # Check for match