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I try to change MTU to 9000 on my sonicwall

I try to change MTU of my Sonicwall nsa2400 from 1500 (default value) to 9000, but if i apply changes show me this error "MTU- Error, Mtu must be a value between 580-1500 in increments of 8"
Anyone knows what i doing wrong?

Thanks for your time!
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Xavi Gelada
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Xavi Gelada
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1 Solution
 
Andy MIT Systems ManagerCommented:
Why are you trying to change the MTU to 9000?

As far as I know the warning is correct - the highest an MTU can be set as is 1500 as this is the largest packet allowed at the network layer.
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Xavi GeladaAuthor Commented:
Because i have a giga ports on my switch, and jumbo frames is enable on it and in other host, switches, san storage, etc

I change all to 9000, but i can't change on the sonicwall.
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giltjrCommented:
I don't think the NSA 2400 support Jumbo frames.  Is there a special reason why you want the firewall set to 9K frames?  

Typically Jumbo frames are limited to the same IP subnet/VLAN.
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Xavi GeladaAuthor Commented:
Technically SonicOS 6.2 enable jumbo frames on SonicWall, but i don't think NSA 2400 supports 6.2 version, i have 5.9 version.

If enable jumbo frames i can sending up to 9000 fragment.
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giltjrCommented:
Technically I never said anything about the level of firmware.

I now what jumbo frames are and what they can do.  Not all hardware supports jumbo frames and not all hardware that support jumbo frames can support jumbo frames of 9000 bytes.  

Again, why do you want the NSA 2400 to support jumbo frames?  The Internet does not support jumbo frames and you DON"T want your firewall to incur the overhead of fragmenting 9000 byte frames down to 1500 bytes.

So the only reason a firewall would need to be configured to support jumbo frames is if you had two internal LAN segments that were separated by this firewall and you wanted to use jumbo frames between the two.
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Xavi GeladaAuthor Commented:
I try to explain better,

If i have and ISP accept MTU 9000 connect directly to my sonicwall, why not sending to 9k mtu?
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giltjrCommented:
I will try to explain it as simply as possible.

Your device does not support jumbo/9k frames.  If you want to support frames larger that 1500 bytes, you will need to replace your current device with one that supports jumbo frames.

However, just as a F.Y.I, the "Internet" does not support jumbo frames.  So even if your ISP were to accept jubmo frames  they will have to fragment to forward on to any other host on the Internet.
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