Policy compression

The following guidelines and limitations apply to policy compression:

• Policy compression disables statistics for individual filter rules. Identical filter rules from different contracts share ternary content-addressable memory (TCAM) space, so the system does not retain statistics for each rule. Enabling policy compression for a contract discards any existing individual rule statistics.

  To retain individual rule statistics for a contract, do not enable policy compression for that contract.

• Policy compression is supported on Cisco Nexus 9300-FX and later platforms.

• Policy compression applies only to user-defined rules. You cannot enable policy compression for implicit rules that the Cisco APIC creates.

• Policy compression applies only to permit and permit-log rules. The system ignores the policy compression setting for copy, redir, deny, and deny-log rules.

• You cannot enable policy compression on contracts that have labels or subject exceptions associated with them.

• Policy compression applies only to contracts for which it is explicitly enabled. If multiple contracts use the same filter, enable policy compression on each contract that you want to compress.

• You can enable policy compression on only one contract for each EPG pair.

• The size of the table that maps source and destination classes to labels depends on the policy profile. For scale information, see the Verified Scalability Guide.

  When the table is full, the system stores additional contracts in uncompressed format.

  To view the current capacity usage in the Cisco APIC GUI, choose Operations > Capacity Dashboard > Leaf Capacity.

• TCAM space is not reduced unless policy compression is enabled. The system dynamically partitions TCAM space when the feature is enabled. If you delete all rules that have policy compression enabled, the system returns the allocated TCAM space.

• If policy compression and bidirectional contracts are both enabled, the compression logic selects the contract that provides the greatest compression.

  Policy compression takes priority over bidirectional contract compression. If the label table is exhausted or lookup collisions occur, the system falls back to bidirectional contract compression.

• When a switch with many rules reloads, the rules remain uncompressed until the switch receives the end-of-bootstrap indication.

• When you upgrade to release 4.0(1) and enable policy compression, delete and reconfigure the contracts if the source release is 3.2(1) or later.

• When you upgrade to release 4.0(1) and enable policy compression, delete and reconfigure the contracts and filters if the source release is earlier than 3.2(1).