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3750G stack slow performance

Koevi Vong
Level 1
Level 1

Hi,

I am currently having performance issues running a 3 x stack 3750G (different models) as a core for a network of roughly 12 x distribution switches.

Switch Ports Model              SW Version            SW Image

------ ----- -----              ----------            ----------

*    1 12    WS-C3750G-12S      12.2(50)SE5           C3750-IPBASE-M

     2 52    WS-C3750G-48PS     12.2(50)SE5           C3750-IPBASE-M

     3 52    WS-C3750G-48PS     12.2(50)SE5           C3750-IPBASE-M

As above, I have a 12 port Fibre switch and 2 x 3750G-48 port switches.

I received this error:

%PLATFORM_UCAST-6-PREFIX:  One or more, more specific  prefixes could not be programmed into TCAM and are being covered by a  less specific prefix

Isuues are:

-high latency and spikes when trying to ping internal servers

-High CPU Utilization, average of ~45-50%

-Very slow performance overall

I believe the slow performance is due to the SDM Template. The SDM Template i am currently running is: desktop VLAN, which was on by default.

The current template is "desktop vlan" template.

The selected template optimizes the resources in

the switch to support this level of features for

8 routed interfaces and 1024 VLANs.

  number of unicast mac addresses:                  12K

  number of IPv4 IGMP groups + multicast routes:    1K

  number of IPv4 unicast routes:                    0

  number of IPv4 policy based routing aces:         0

  number of IPv4/MAC qos aces:                      0.5K

  number of IPv4/MAC security aces:                 1K

I tried to change the SDM to route but hit another issue where the 3750g-48 does not support SDM route so I had to revert back to desktop VLAN.

Could the SDM Template be the reason for slow performance? If so which SDM Template should i use as this is the Core L3 switch.

1 Accepted Solution

Accepted Solutions

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The  Author of this posting offers the information contained within this  posting without consideration and with the reader's understanding that  there's no implied or expressed suitability or fitness for any purpose.  Information provided is for informational purposes only and should not  be construed as rendering professional advice of any kind. Usage of this  posting's information is solely at reader's own risk.

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Posting

Try either "sdm prefer default desktop" or "sdm prefer routing desktop", and if accepted, then reload.

View solution in original post

5 Replies 5

Joseph W. Doherty
Hall of Fame
Hall of Fame

Disclaimer

The Author of this posting offers the information contained within this posting without consideration and with the reader's understanding that there's no implied or expressed suitability or fitness for any purpose. Information provided is for informational purposes only and should not be construed as rendering professional advice of any kind. Usage of this posting's information is solely at reader's own risk.

Liability Disclaimer

In no event shall Author be liable for any damages whatsoever (including, without limitation, damages for loss of use, data or profit) arising out of the use or inability to use the posting's information even if Author has been advised of the possibility of such damage.

Posting

3750G models do support a routing SDM template, but the -12S supports SDM templates unique to it.  I recall in a mixed stack of 12S and other 3750 models, you shouldn't use 12S SDM templates.  So, I'm wondering whether you were, perhaps, invoking a 12S routing SDM template.  What are all your SDM template options?

PS:

And yes, if you overflow TCAM resources, a 3750's performance will generally very much degrade.

Hi,

Thanks for your respone, from memory the options for SDM were:

SDM prefer Access/Vlan/Routing/Default or desktop.

Not too sure what the desktop command does but its an option after selecting one of the four options, for e.g;

(config)# SDM prefer default desktop

OR

(config)# SDM prefer default

^Found out the answer to the desktop command, see below;

There are two versions of each template: a desktop  template and an aggregator template. The Catalyst 3750-12S switch can  use the larger TCAM size available in the aggregator templates or can  use the standard desktop templates. All other Catalyst 3750 switches  support only the desktop templates. If you do not enter the desktop keyword on an aggregator switch, the aggregator templates are selected.

Source:

http://www.cisco.com/en/US/docs/switches/lan/catalyst3750/software/release/12.2_55_se/configuration/guide/swsdm.html

Disclaimer

The  Author of this posting offers the information contained within this  posting without consideration and with the reader's understanding that  there's no implied or expressed suitability or fitness for any purpose.  Information provided is for informational purposes only and should not  be construed as rendering professional advice of any kind. Usage of this  posting's information is solely at reader's own risk.

Liability Disclaimer

In  no event shall Author be liable for any damages whatsoever (including,  without limitation, damages for loss of use, data or profit) arising out  of the use or inability to use the posting's information even if Author  has been advised of the possibility of such damage.

Posting

Try either "sdm prefer default desktop" or "sdm prefer routing desktop", and if accepted, then reload.

Problem resolved today, issued "sdm prefer default desktop" and everything is running smoothly.

Thanks

Disclaimer

The   Author of this posting offers the information contained within this   posting without consideration and with the reader's understanding that   there's no implied or expressed suitability or fitness for any purpose.   Information provided is for informational purposes only and should not   be construed as rendering professional advice of any kind. Usage of  this  posting's information is solely at reader's own risk.

Liability Disclaimer

In   no event shall Author be liable for any damages whatsoever (including,   without limitation, damages for loss of use, data or profit) arising  out  of the use or inability to use the posting's information even if  Author  has been advised of the possibility of such damage.

Posting

Great!  In that case, you might want to mark this issue as correctly answered, so others may know it might be used if they have a similar problem.

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