Cisco SDM (Switching Database Manager)

This topic is to discuss the following lesson:

In my years of working with multi-layer switches I never knew these templates existed, thanks!

Hi Emir,

Good to hear you learned something :slight_smile: Might be nice to check some of your production switches, see if their current SDM template is suitable for the job.

Rene

Renee,

Do you know if nx-os has similar feature?

Thanks

Hi Anuj,

It does, you can try the show hardware profile status command and the hardware profile command in configuration mode.

Rene

Hi @ReneMolenaar

I have couple of questions :-

1-
Is SDM template just for TCAM or for both TCAM and CAM ? If it’s just for TCAM what is the need of storing unicast mac addresses since they are stored in CAM table ?

2-
Does layer two switch have TCAM table ?

3-
What are the uses of masks that used by unicast mac addresses, since mac address values need to be exact match to make forward decision ?
Untitled

Hi Hussein,

It’s for both, you can verify this by looking at the SDM template and MAC address table of the switch:

SW1#show sdm prefer | include unicast mac
  number of unicast mac addresses:                  8K

SW1#show mac address-table count | include Space
Total Mac Address Space Available: 8048

An L2 switch still has a TCAM table, they can do things like access-lists where we also use the TCAM.

You can see the content of the TCAM table for L2 entries with show platform tcam table l2 detail or show platform tcam table mac-address detail.

For some MAC addresses, it shows the mask (FFFF.FFFF.FFFF) which is an exact match.

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Very useful extra information
thank you very much sir

Hi Renee,

Is there any specif models of Switch support SDM. I have tried vIOS L2 image in Eve-ng and could not run Sh SDM Prefer?

Thanks

Got SDM command in Packet tracer. must be the image is not a multi-layer switch image. Can you please suggest what image I can use as Multi-layer switch in GnS3 or eve-ng.

Now in Packet tracer there is no Template under SDM prefer :frowning:

Hello Mohit

SDM is a feature that manages CAM and TCAM on a physical device. It doesn’t actually change the way a device will operate. Virtual devices on GNS3 don’t have CAM and TCAM, so there is nothing to manage. Remember GNS3 is an emulator, which means it runs real IOS operating systems on your computer hardware. The computer hardware doesn’t have CAM and TCAM, so the feature itself cannot function.

In order to see these features in action you will have to either use a simulator like Packet Tracer, which simulates the existence of these memory types and responds appropriately, (but only to a certain extent as you can see) or you must use real hardware.

Most L3 switches have this feature including the 3750, as well as the higher 4500/4600/9400 and 6500/6600/9600 series catalyst chassis switches.

You can find out more about SDM and GNS3 at this GNS3 forum thread.

I hope this has been helpful!

Laz

Quick question: Is SDM used for Cisco routers at all, or just switches? If not, is there a similar protocol for routers?

Thanks!

Hello Louis

The purpose of SDM is to be able to more appropriately manage memory that is used by a multilayer switch due to the fact that memory is used for both Layer 2 operations as well as Layer 3. Because a router has only layer 3 functionality, it has no need for a similar memory management feature.

Layer 3 switches, depending on how they are employed in your network design, may focus more on L3 operations, or L2 operations.

If L3 operations are highly utilized, then much memory is being wasted by allocating space for L2 operations that are not in much use. Similarly, if L2 operations are highly utilized, then much memory is being wasted by being allocated for L3 operations that are not used very much. SDM templates are applied to more efficiently use allocated memory depending on how you employ the device.

Since routers only allocate memory for L3 operations, no similar memory management feature is necessary.

I hope this has been helpful!

Laz

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20201214_015742

  1. Why are all tcam utilization values being MAX??
  2. How to check tcam utilization in C9200?

Hello YongHun

Actually, they’re not being maxed out. The first column is titled Max Masks/Values. This column shows the maximum number of masks and the maximum number of values that can be stored for each category. A mask can be used to reference a range of addresses and takes up space in the TCAM. So for unicast MAC addresses, you can have 32988 masks and 32988 values. Although this is outside the scope of the lesson, you can find out more about the types of TCAM used for masks and values at the following link:

Now the Used Masks/values column is what you have actually used in the device. So out of the 32988/32988 maximum, you’ve used only 52/52. The same is true for the rest of the values.

Now it is interesting that for both Max and Used values, you seem to have the same number of masks and values. I believe this has to do with the chosen SDM template and the platform you are using.

I hope this has been helpful!

Laz

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