ONS 15454 and ONS 15454 SDH Ethernet Configuration Guide R8.5.1 -- Configuring the Switching Database Manager

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This chapter describes the switching database manager (SDM) features built into the ML-Series card and contains the following major sections:


Understanding the SDM

ML-Series cards use the forwarding engine and ternary content-addressable memory (TCAM) to implement high-speed forwarding. The high-speed forwarding information is maintained in TCAM. The SDM is the software subsystem that manages the switching information maintained in TCAM.

SDM organizes the switching information in TCAM into application-specific regions and configures the size of these application regions. SDM enables exact-match and longest-match address searches, which result in high-speed forwarding. SDM manages TCAM space by partitioning application-specific switching information into multiple regions.

TCAM identifies a location index associated with each packet forwarded and conveys it to the forwarding engine. The forwarding engine uses this location index to derive information associated with each forwarded packet.

Understanding SDM Regions

SDM partitions multiple application-specific regions and interacts with the individual application control layers to store switching information. The regions share the total available space. SDM consists of the following types of regions:

  • Exact-match region-The exact-match region consists of entries for multiple application regions such as IP adjacencies.
  • Longest-match region-Each longest-match region consists of multiple buckets or groups of Layer 3 address entries organized in decreasing order by mask length. All entries within a bucket share the same mask value and key size. The buckets can change their size dynamically by borrowing address entries from neighboring buckets. Although the size of the whole application region is fixed, you can reconfigure it.
  • Weighted-exact-match region-The weighted-exact-match region consists of exact-match-entries with an assigned weight or priority. For example, with QoS, multiple exact match entries might exist, but some have priority over others. The weight is used to select one entry when multiple entries match.

Table 15-1 lists default partitioning for each application region.

Table 15-1: Default Partitioning by Application Region
Application Region Lookup Type Key Size Default Size

IP Adjacency


64 bits

300 (shared)

IP Prefix


64 bits

300 (shared)

QoS Classifiers

Weighted exact-match

64 bits

300 (shared)

IP VRF Prefix

Longest prefix match

64 bits

300 (shared)

IP Multicast

Longest prefix match

64 bits

300 (shared)

MAC Addr

Longest prefix match

64 bits


Access List

Weighted exact match

64 bits

300 (shared)

Configuring SDM

This section describes SDM region size and access control list (ACL) size configuration. The commands described in this section are unique to the switching software. Configuration changes take place immediately on the ML-100T-8 card.

Configuring SDM Regions

To configure SDM maximum size for each application region, perform the following procedure, beginning in global configuration mode:

Step Command Purpose


ML_Series(config)# sdm size region-name number-of-entries

Configures the maximum number of entries for an SDM region.


ML_Series(config)# end

Exits to privileged EXEC mode.

An example of this is shown in Example 15-1.

Example 15-1: Limiting the IP-Prefix Region to 2K Entries
ML_Series # configure terminal
ML_Series(config)# sdm size ip-prefix 200
ML_Series(config)# end 

Configuring Access Control List Size in TCAM

The default maximum size of the ACL is 300 64-bit entries. You can enter the sdm access-list command to change the maximum ACL database size, as shown in Table 15-2.

Table 15-2: Partitioning the TCAM Size for ACLs
Task Command

sdm access-list number-entries

Sets the name of the application region for which you want to configure the size. You can enter the size as an absolute number of entries.

An example of this is shown in Example 15-2.

Example 15-2: Configuring Entries for the ACL Region in TCAM
ML_Series# configure terminal 
ML_Series(config)# sdm access-list 100
ML_Series(config)# end  

Monitoring and Verifying SDM

To display the number of available TCAM entries, enter the show sdm size command from global configuration mode:

ML_Series # show sdm size

Active Switching Database Region Maximum Sizes :

IP Adjacency  : 300 64-bit entries

IP Prefix  : 300 64-bit entries

QoS Classifiers  : 300 64-bit entries

IP VRF Prefix  : 300 64-bit entries

IP Multicast  : 300 64-bit entries

MAC Addr  : 8192 64-bit entries

Access List  : 300 64-bit entries

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