Table of Contents

Configuring Switching Database Manager

This chapter describes the switching database manager (SDM) features built into your switch router. This chapter includes the following topics:

The information in this chapter applies to the Catalyst 8540 CSR and Catalyst 8540 MSR with Layer 3 functionality. For further information about the commands used in this chapter, see the ATM and Layer 3 Switch Router Command Reference.

About Switching Database Manager

The enhanced Gigabit Ethernet interfaces use the forwarding engine and the ternary content addressable memory (TCAM) to implement the Layer 2 and Layer 3 functionality. The Layer 2 and Layer 3 switching information is maintained in TCAM. The switching database manager (SDM) is the Layer 3 software subsystem that manages the Layer 3 switching information maintained in TCAM.

SDM resides on the central processor and its primary function is to maintain the Layer 3 switching database. SDM maintains the address entries contained in TCAM in an appropriate order. SDM manages TCAM space by partitioning protocol-specific switching information into multiple regions.

The forwarding engine on the enhanced Gigabit Ethernet interfaces performs packet processing on multiple channels simultaneously and extracts the packet header information. It uses this packet header information to issue exact-match or longest-match address searches in the switching information stored in TCAM.

TCAM identifies the location index of the Layer 2 or Layer 3 address and conveys it to the forwarding engine. The forwarding engine uses this location index to further derive information associated with each Layer 2 and Layer 3 address.

The key benefits of SDM in Layer 3 switching are its ability to organize the switching information in TCAM into protocol- specific regions and its ability to configure the size of these protocol regions. SDM enables exact-match and longest-match address searches, which result in high-speed forwarding.

About SDM Regions

SDM partitions TCAM space into multiple regions. Each region is protocol specific. SDM interacts with the individual protocol control layer to store Layer 3 switching information. SDM consists of the following types of regions:

The enhanced Gigabit Ethernet interface module supports TCAM sizes of 32 KB, 64 KB, or 256 KB. Each entry in TCAM is 32 bits wide. Since SDM is responsible for managing TCAM space, SDM partitions the entire TCAM space for each protocol region based on user configuration. A change in the partition configuration takes effect only during the next system reboot.

Table 12-1 lists default partitioning for each protocol region in TCAM.

The enhanced Gigabit Ethernet interface module is available with 32 KB, 64 KB, or 256 KB TCAM space. You can configure the various protocol regions in TCAM based on your requirements and on the size of TCAM on your Gigabit Ethernet interface module.

Note   The enhanced Gigabit Ethernet interface module is available with 32 KB, 64 KB, or 256 KB TCAM space. The maximum SDM size is equal to the lowest TCAM size available among the interface modules present at the time of booting up the switch router. For example, if you have two interface modules with 64 KB and 256 KB TCAM sizes, then the maximum SDM size is 64 KB based on the lowest TCAM size available at bootup.

Configuring SDM

This section describes the commands necessary to configure SDM. It includes commands necessary to configure the autolearn feature in SDM, commands required to configure the size of the SDM regions, and commands required to configure the size of the access-list region in the TCAM. The commands described in this section are unique to Layer 3 switching software.

Configuring SDM autolearn

SDM groups entries based on their mask lengths into "buckets." The size of each bucket in the protocol region varies. The autolearn feature in SDM automatically saves the mask length distribution (bucket size distribution) for the longest-match region in the switching database. SDM uses this information to set up the partitions, which are effective during the next system reboot.

Layer 3 switching enables the autolearn feature by default. The no form of the sdm autolearn command disables the SDM autolearn feature. You can reenable autolearn by issuing the sdm autolearn command from global configuration mode, as shown in the following example:

Configuring SDM Regions

The protocol region size in SDM is represented by the number of 32-bit or 64-bit entries. The combined size of all the application regions should be calculated in terms of 32-bit TCAM entries and should not exceed the total TCAM size. The enhanced Gigabit Ethernet interface module supports TCAM sizes of 32 KB, 64 KB, or 256 KB.

Note   Although the size of the whole protocol region is configured by default, you can reconfigure it. The reconfigured size of the protocol region is effective only at the next system reboot.

To configure SDM size for each protocol region, use the following steps, beginning in global configuration mode:

Example

The following output is an example of configuring 2048 entries for the ip-prefix region.

The combined size entered for all the protocol regions should not exceed the total TCAM size. To display the supported size of SDM, use the show sdm size current command from global configuration mode.

To display the configured size of SDM, use the show sdm size configured command from global configuration mode.

Note   When you make changes to the SDM configuration, it shows up in the show sdm size configured display and takes effect on next reload.

You can use the show sdm internal command to get SDM management information for each protocol region in TCAM.The information includes SDM status, minimum TCAM size available, and the TCAM size required for your current configuration. For each application region, this command also yields information about the logical start and end of the application region in TCAM, lookup type, key size, and statistics about other key operations.

To obtain SDM management information for each protocol region in TCAM, use the following command:

Example

The following output is an example of SDM management information for the show sdm internal all-region command:

For additional information on the show sdm internal command syntax, refer to the sdm commands in the ATM and Layer 3 Switch Router Command Reference .

Configuring Access List Size in TCAM

The enhanced Gigabit Ethernet interface module supports TCAM sizes of 32 KB, 64 KB, or 256 KB. The combined size of the protocol regions and access lists should not exceed your TCAM space. The default size of the access lists in a 32 KB, 64 KB, or 256 KB TCAM is 512. You can use the sdm access-list command to partition the TCAM space for access lists.

To partition the TCAM space for access lists, use the following command:

Before you configure the access-list region in TCAM, make sure that TCAM has enough space to accommodate the access-list region. Use the show internal all-regions command to verify how much space is available in TCAM.

Example

The following output is an example of configuring 8192 entries for the access list region in TCAM:

Router(config)# end