1. Overview
1.1. SDM manages L2 and L3 switching info
1.1.1. Maintained on Ternary Content Addressable Memory (TCAM)
1.1.1.1. Used for forwarding lookups
1.2. TCAM designed for rapid table lookups by the ACL engine
1.2.1. ACL engine determines how switch handles packet
1.2.1.1. permitted
1.2.1.2. denied
1.2.2. Limited amount of entries
1.3. Issues
1.3.1. Resource contention
1.3.2. Resource exhaustion
1.4. SDM stands for Switching Database Manager
2. Architecture
2.1. TCAM
2.1.1. Can be shared between L2 and L3
2.1.1.1. Forwarding entries
2.1.1.2. RACLs
2.1.1.3. VACLs
2.1.1.4. QoS ACLs
2.1.2. Most switches have one TCAM
2.2. Table Structure
2.2.1. Layer 2 Learning
2.2.1.1. Port learning policies
2.2.2. Layer 2 Forwarding
2.2.2.1. Learned unicast and multicast addresses
2.2.3. Layer 3 Routing
2.2.3.1. Used for unicast and multicast route lookups
2.2.4. ACL and QoS table
2.2.4.1. Identifying traffic according to security and QoS ACLs
3. SDM Templates
3.1. Three predefined templates
3.1.1. Routing Template
3.1.1.1. Maximizes resources for unicast routing
3.1.1.2. When switch is used as a router or route aggregator
3.1.2. VLAN Template
3.1.2.1. Unicast routing disabled
3.1.2.2. Allows max number of supported MAC addresses
3.1.2.3. When switch is purely a L2 device
3.1.3. Default Template
3.1.3.1. Mix between routing and VLAN template
3.2. Two versions of each template
3.2.1. Desktop Template
3.2.2. Aggregator Template
3.2.2.1. Limited to specific switches
3.3. Switch reload required to use a new SDM template
3.4. Switch Stack
3.4.1. SDM template on master overrides a newly added switch
4. Resource Exhaustion
4.1. Results of resource exhaustion
4.1.1. L2 forwarding and learning
4.1.1.1. New learned addresses are flooded to all ports within the ingress VLAN
4.1.2. L3 routing
4.1.2.1. L3 unicast and multicast routes learned only in software and not in TCAM
4.1.2.1.1. Slower routing
5. Configuration
5.1. Show commands
5.1.1. show sdm prefer
5.1.2. show sdm prefer vlan
5.2. To change SDM template
5.2.1. conf t
5.2.2. sdm prefer vlan / sdm prefer routing
5.2.3. reload