MTU Configuration

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Oct 12th, 2009
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Hi,


Just want to ask what is the effect of configuring a higher MTU size besides higher throughput. Do i Have to configuring all my switches to have the same mtu sizes or those only that uses it?


Thanks.

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Joseph W. Doherty Mon, 10/12/2009 - 17:23
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"Just want to ask what is the effect of configuring a higher MTU size besides higher throughput."


Often less work on the forwarding engine, since much of the work is per frame/packet.


"Do i Have to configuring all my switches to have the same mtu sizes or those only that uses it?"


As long as other switches won't see the larger MTU frames, don't believe you need to configure them too.

rc.castillo Mon, 10/12/2009 - 17:37
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Hi Joseph,


the path that the packet will traverse will be the one that i'll be configuring is that what you mean? And also will it affect the machines that do not support jumbo frames?



Lucien Avramov Mon, 10/12/2009 - 17:34
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When you increase the MTU make sure you do to the devices interconnected, in your case I presume switches.


If one device has a smaller MTU than the other, it will cause fragmentation.


For reminder, MTU: Is the maximum packet size, in bytes, that can be transmitted across a link. The MTU determines the size of your packets, so if it is too small, your computer will be responding often. If it is too big, errors will cause each packet to be resent or there will be fragmentation.



rc.castillo Mon, 10/12/2009 - 17:50
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Hi Sir,


for example i configured a port on a 6500 to haave an mtu of 9000. All the switches that will be cascaded via this port should also be configured with that mtu, and all of the computer/servers connected via this switches should also have an mtu of 9000? am i correct?

Lucien Avramov Mon, 10/12/2009 - 17:51
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Yes that is correct.

But why do you want an mtu of 9000? What are you really trying to achieve?

rc.castillo Mon, 10/12/2009 - 17:55
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hi Sir,


I'm trying to have a higher throughput on my servers. Is it advisable?


Thanks.

Lucien Avramov Mon, 10/12/2009 - 18:52
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Not sure. Is the communication only between the servers, or goes to clients over for example a WAN link?


rc.castillo Mon, 10/12/2009 - 19:19
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hi sir,


Its for local area clients, server to server communications and over the WAN clients. Is it possible?

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