Filter Policies
Router Configuration Guide 483
Figure 17 depicts how the IOM/CPM filter policy illustrated at the top of this section changes
with a filter match list usage (using IPv4 address prefix list in this example).
Figure 17: IOM/CPM Filter Policy Using an Address Prefix Match List
The hardware resource usage does not change whether filter match lists are used or whether
operator creates multiple entries (each per one element of the list): however, a careful
consideration must be given to how the lists are used to ensure only desired match
permutations are created in a filter policy entry (especially when other matching criteria that
are also lists or ranges are specified in the same entry). The system verifies that a new list
element, for example, an IP address prefix, cannot be added to a given list or a list cannot be
used by a new filter policy unless resources exist in hardware to implement the required filter
policy (ies) that reference that list. If that is not the case, addition of a new element to the list
or use of the list by another policy will fail.
Some use cases like those driven by dynamic policy changes, may result in acceptance of
filter policy configuration changes that cannot be programmed in hardware because of the
resource exhaustion. If that is the case, when attempting to program a filter entry that uses a
match list(s), the operation will fail, the entry will be not programmed, and a notification of
that failure will be provided to an operator.
Refer to the SR OS Release Notes for information about objects that can be grouped into a
filter match list for FP and CPM filter policies.
Entry K
match: IPv4 Prefix List A
CPM Filter
IOM Filters
OSSG730
Entry M
match: IPv4 Prefix List A
IPv4 Prefix 1
IPv4 Prefix 2
IPv4 Prefix N
IPv4 Prefix List A
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