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Beginner

SG 200-08 Not Allowing Jumbo Frames

Hi,

 

I've enabled 9000 MTU everywhere I could on this switch, but I can't ping greater than 1500.  I imagine that this could be due to a DoS prevention, but there's no setting to turn that off!  What am I missing?

Running version 1.0.8.3

 

Thanks

8 REPLIES 8
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Cisco Employee

Hi Askhaan,

 

Please check your PC NIC advanced settings as well as OS settings. for windows that would be:

netsh interface ipv4 show subinterfaces

Regards,

Aleksandra

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I can confirm this is an issue as well.  When I remove the SG200-08P from the mix I can ping with >1514 MTU sizes.  Put it back in and nothing.  Ports are set to 9216 MTU on the switch.

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Also, under RMON, the oversize packets counter increases with my sent ICMP packets.

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This seems to be limited to ICMP packets. I did verify I could push jumbo frame through via watching streams on wireshark.

 

Here's a thread saying the ICMP limit is "as designed".

https://supportforums.cisco.com/discussion/11262811/sg-200-08-jumbo-frames-not-forwarded

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Is there no way to correct this design flaw?

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From my understanding, this only affects ICMP packets.  It has been a "feature" since the unit was initially released years ago.  Some kind of DOS protection.

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I get that, but how do we turn it off?

The SG300 works perfectly.

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By "feature" I mean it can be considered a bug to some people.  There is no way to turn it off.

You are able to pass frames larger than 1518 bytes as long as they aren't ICMP packets.  My SG200-28P works as expected with ICMP like the SG300.  Seems this 8 port version is really a different breed from the other 200 series.  Like an adopted cousin.