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Re: can I ask mtu question
From: "Justin M. Streiner" <streiner () cluebyfour org>
Date: Fri, 30 Jan 2009 16:51:00 -0500 (EST)

On Fri, 30 Jan 2009, Ricky Beam wrote:

On Fri, 30 Jan 2009 12:57:25 -0500, adrian kok <adriankok2000 () yahoo com hk> wrote:
What is max mtu in jumbo frame?

That depends on the hardware. I've seen gear running as low as ~8k. I'd have to consult standard, but I think the max is 10k (10240).

Keep in mind the switch is not the only device on the network with jumbo frame limits. The NICs in your servers will also have limits.

Do I need to reboot the switch to take effect after
setting up it?

Again, this depends on the system. Many accept the change immediately, while others have to rebooted or interfaces reset to effect the change.

if it doesn't need to reboot, How can I know the
switch is running fine in this mtu 9000? eg: cisco
any tools to check?

"ping" will do. Set the packet size larger than the normal MTU (1500) and see if it crosses the network intact. If it's not working, A) the packets will be dropped, and B) the "oversized frame" counter (among others) should be clocking errors.

If you're sourcing the pings from a device that supports it, you can also send the large pings with the Do Not Fragment bit set.

jms


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