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upower3
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CRS312-4C+8XG and Jumbo Frames

Wed Dec 04, 2019 4:05 pm

Hello,

we just brought CRS312-4C+8XG mainly for test purpose to see if it so good as it appears from reviews and if we can use it as iSCSI switch. So to say, even SwOS is ok for this purpose so far (really basic packet forwarding and some stats), but I simple can not manage to change MTU to use Jumbo Frames.

So the question is: if it is possible to run Jumbo Frames on CRS312-4C+8XG in SwOS (I suspect so, at lease under ROS I can change L2 MTU to 12K+), and how to do that.

P.S. Yes ROS is an option but I'd prefer to have something fast-boot and no extra options at all as SwOS for this simple task (so less code is less problems).
 
Zacharias
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Re: CRS312-4C+8XG and Jumbo Frames

Wed Dec 04, 2019 10:41 pm

Here you can find the max l2mtu per device...
https://wiki.mikrotik.com/wiki/Manual:M ... uterBoards
 
upower3
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Re: CRS312-4C+8XG and Jumbo Frames

Wed Dec 04, 2019 10:54 pm

Here you can find the max l2mtu per device...
https://wiki.mikrotik.com/wiki/Manual:M ... uterBoards
Yes I can. But what I need to know is how to change it in SwOS, for I can't see any options there for MTU at all.
Any help with that?
 
mkx
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Re: CRS312-4C+8XG and Jumbo Frames

Wed Dec 04, 2019 11:01 pm

But what I need to know is how to change it in SwOS, for I can't see any options there for MTU at all.

L3 MTU is something that routers and/or end devices has to deal with. Max L2 MTU is basically HW property and not something that should be lowered.

But check also this thread, the last post is indicative: viewtopic.php?t=124048
BR,
Metod
 
Zacharias
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Re: CRS312-4C+8XG and Jumbo Frames

Thu Dec 05, 2019 3:49 am

@mkx the wiki link i posted earlier shows the max l2mtu for CRS312...
 
upower3
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Re: CRS312-4C+8XG and Jumbo Frames

Thu Dec 05, 2019 8:26 am

@mkx the wiki link i posted earlier shows the max l2mtu for CRS312...
I know the switch is capable to work with 10k packets, but SwOS seems to use standart (1500) MTU only, and I see no options to change it. I can change it in ROS, but prefer to use SwOS.

So basically I try to find a way to set up ports to pass say 9K or 10K packets to speed up iSCSI.

Any ideas?
 
mbovenka
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Re: CRS312-4C+8XG and Jumbo Frames

Thu Dec 05, 2019 8:32 am

Just a wild idea: assuming for a moment that SwOS leaves the MTU as it finds it, you could boot into RouterOS, change the MTU, and boot back into SwOS.
 
upower3
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Re: CRS312-4C+8XG and Jumbo Frames

Thu Dec 05, 2019 8:41 am

Just a wild idea: assuming for a moment that SwOS leaves the MTU as it finds it, you could boot into RouterOS, change the MTU, and boot back into SwOS.
Will try but this won't looks like serious approach: what if I reboot switch one day (power outage) and MTU become the default one while clients will expect bigger one?

Seems like ROS is the only options, even that switch control there is somewhat mystic for me :)
 
mbovenka
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Re: CRS312-4C+8XG and Jumbo Frames

Thu Dec 05, 2019 9:10 am

Yes, you should definitely test a poweroff. Boot RouterOS, set the MTU, set it to boot SwOS, and powercycle it. Does it still work?: You're golden. If not (and, to be honest, I'm betting it won't ;-)), well, it was worth a shot.
 
EdPa
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Re: CRS312-4C+8XG and Jumbo Frames

Thu Dec 05, 2019 9:15 am

CRS312 device booted in SwOS by default supports jumbo frames up to 10218 bytes and you cannot change it to other values. It is the same for all CRS3xx devices booted in SwOS.

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