3Com CoreBuilder 3500, Руководство по внедрению

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254 C
HAPTER
10: P
ACKET
F
ILTERING
Combining All the Filters
Together, the packet filters work to perform the solution to the problem:
filtering the broadcast packets from the market data servers. These steps
show how to create this filter:
1 Name the filter:
name “Discard XNS & IP broadcast pkts w/in socket range”
2 Perform steps 2 through 8 as described earlier in “Packet Filter One . ”
3 Perform steps 2 through 8 as described earlier in “Packet Filter Two.”
4 Add an and statement to compare the results of step 2 and the results of
step 3:
and
# compare if XNS & in range
5 Perform steps 2 through 4 as described earlier in “Combining a Subset of
the Filters.”
6 Add an or statement:
or
# determine if the type field is either XNS or IP
7 Add a
not
statement to discard any matching packets:
not
# discard if (IP & in range) or (XNS & in range)
The complete packet filter discards IP and XNS packets that are within the
specified range.
Optimizing the Filter
with Accept and
Reject Commands
The following combination filter performs the same function but uses the
accept
,
reject
, and
pushTop
commands to exit the filter as soon as
possible to save processing time.