Recently the topic came up on the Cisco Learning Network on OSM ratio’s for the 18/4 module. Here is a summary of many of the ratios for various modules as well as some handy notes:
Generation 2 Switches and Modules
9216 does not support Gen-2 modules
If dedicated ports are not using all of their allocated bandwidth, the unused bandwidth is made available for use by all ports configured for shared bandwidth mode.
Performance Buffers are used on 12-port 4GB, 4-port 10GB modules only.
Port Groups
| Module | Ports Per Group | Bandwidth Per Group | Max BW Per Port | Dedicated | Shared |
| DS-X9148 | 12 | 12.8 | 4GB | Yes | Yes |
| DS-X9124 | 6 | 12.8 | 4GB | Yes | Yes |
| DS-X9304-18K9 | 6 | 12.8 | 4GB | Yes | Yes |
| DS-X9112 | 3 | 12.8 | 4GB | Yes | No |
| DS-X9704 | 1 | 10 | 10GB | Yes | No |
| DS-C9134-K9 | 4 | 16 | 4GB | Yes | Yes |
| 1 | 10 | 10GB | Yes | No | |
| DS-C9124-K9 | 4 | 16 | 4GB | Yes | No |
| DS-C9222i-K9 | 6 | 12.8 | 4GB | Yes | Yes |
| 48-port Module 4:1 – 5:1 | |||||
| BB Credit Allocation Type | BB Credit Per Module | Dedicated (2-250) | Shared (2-16) | ||
| ISL | Fx | ISL | Fx | ||
| User Defined BB | 6000 | 125 | 16 | 16 | 16 |
| 24-port Module 2:1 – 4:1 | |||||
| BB Credit Allocation Type | BB Credit Per Module | Dedicated (2-250) | Shared (2-16) | ||
| ISL | Fx | ISL | Fx | ||
| User Defined BB | 6000 | 250 | 16 | 16 | 16 |
| 18-port Module 2:1 – 4:1 | |||||
| BB Credit Allocation Type | BB Credit Per Module | Dedicated (2-250) | Shared (2-16) | ||
| ISL | Fx | ISL | Fx | ||
| User Defined BB | 4509 | 250 | 16 | 16 | 16 |
| 12-port Module 1:1 | |||
| BB Credit Allocation Type | BB Credit Per Module | Dedicated (2-250) | |
| ISL | Fx | ||
| User Defined BB | 5488 | 250 | 16 |
| Performance | 512 (shared) | 145 | 12 |
With regards to the 12-port module:
There are 2488 extra buffers available as extended BB_credit buffers after allocating all the default BB_credit buffers for all the ports in ISL mode (5488 – (250 * 12)).
Extended BB_credits are allocated across all ports on the switch. That is, they are not allocated by port group.
| 4-port Module 1:1 | |||
| BB Credit Allocation Type | BB Credit Per Module | Dedicated (2-250) | |
| ISL | Fx | ||
| User Defined BB | 5488 | 250 | 16 |
| Performance | 512 (shared) | 145 | 12 |
With regards to the 4-port module:
The ports in the 4-port 10-Gbps switching module only support 10-Gbps dedicated rate mode. FL port mode and shared rate mode are not supported.
There are 4488 extra buffers available as extended BB_credits after allocating all the default BB_credit buffers for all the ports in ISL mode (5488 – (250 * 4)).
| 9134 Switch | |||
| BB Credit Allocation Type | BB Credit Per Port Group | BB Credit Per Port Defaults (2-250) | |
| ISL | Fx | ||
| User Defined BB | 64 | 16 | 16 |
| 9124 Switch | |||
| BB Credit Allocation Type | BB Credit Per Port Group | BB Credit Per Port Defaults (2-250) | |
| ISL | Fx | ||
| User Defined BB | 64 | 16 | 16 |
| 9222i Switch | |||
| BB Credit Allocation Type | BB Credit Per Port Group | BB Credit Per Port Defaults (2-250) | |
| ISL | Fx | ||
| User Defined BB | 4509 | 250 | 16 |
5 Responses to OSM Ratio’s on MDS blades