Jumbo Frame MTU

Unanswered Question
May 26th, 2007


I would like to enable Jumbo frame (>9000 bytes) at my WAN links (POS interface). What would be the recommended MTU for jumbo?



I have this problem too.
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Paolo Bevilacqua Sat, 05/26/2007 - 08:39

What can your hosts and LAN can generate ?

If not bigger than standard, there is no advantage in increasing MTU size.

mazlan.alatif Sat, 05/26/2007 - 19:52


We are going to host grid computing and super computer which will runs applications with bigger MTU packet size. Due to that we need to enable jumbo fram/bigger mtu at our routers interfaces.

So what would be the correct/recommneded number to config into router. mtu 9000 or mtu 9192 or else??


Paolo Bevilacqua Sun, 05/27/2007 - 08:38


Each type of interface can have a different upper maximum. Please specify router type and exact interface model used. You will also need to enable that on the LAN interfaces and switches. Eg, it does not help increasing MTU on the router if the switch that is in between router and host does not support it.

mazlan.alatif Sun, 05/27/2007 - 18:13

Yes, you are correct. the switch itself (LAN) will enable to support jumbo. The routers in the middle are 7606, some GSR12008. The max mtu are diferent. 7606 max mtu is 9216 & GSR is 9180. That is why i tried to find best practise (if any) how to config this.



Paolo Bevilacqua Sun, 05/27/2007 - 18:34

You will be limited by the smaller MTU in the path between hosts, so there is no really best practice other than to find out where this happens in your network and make sure other interfaces are same or better.

mazlan.alatif Sun, 05/27/2007 - 19:18

this host is running and support jumbo frame. so at network side, we must prepare mtu jumbo at router interfaces.

mazlan.alatif Sun, 05/27/2007 - 19:53

yes, this is for LAN side. what i try to find is is there any best practice config for the mtu at WAN interfaces, since diferent int will hv diferent max mtu. so i would like to find recomended and best practise config that succesfully been deployed. i just want the correct max mtu number to be confiured at my router interfaces.

the LAN can generate 9000 bytes, but at my router we will configure more than 9000, ie 9192, 9180. but to config the numbers, i need to find the best practice.



Paolo Bevilacqua Sun, 05/27/2007 - 20:00

Hello, as I said before, first of all different interfaces have different maximum MTU sizes, generally the POS is 9216, beside that there is not really a best practice to recommend, because any value equal or bigger to what is supported by the host and switch will work.


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