i82573L mtu

[v***@gjbi.cz]

Dear all,

please do you know if is possible to change (by load module
or patch kernel) mtu length to 1504? Now is limited to 1500.

Thanks for any answer

Jan


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[Jonathan A. Kollasch]

Post by v***@gjbi.cz
Dear all,
please do you know if is possible to change (by load module
or patch kernel) mtu length to 1504? Now is limited to 1500.
Thanks for any answer

According to the Intel PCIe GbE Controllers Open Source
Software Developer's Manual, section 2.7.1, not all 82573
chips support jumbo frames. The 82573E/82573V do not have
the support while the 82573L has some support but it's
more limited than the regular 82572's support. wm(4)
doesn't differentiate between the various flavors of the
573.

But that doesn't really answer the question,
because it appears ETHERCAP_VLAN_MTU should be
being ORed into ec_capabilities on the 573.

Now, this may not actually allow you to set the MTU to
1504 manually, I guess it could only be an allowance
for the vlan(4) driver to throw in the tag without
reducing the mtu of the vlan interface.

I'd have to look up how ETHERCAP_JUMBO_MTU and
ETHERCAP_VLAN_MTU actually modify the allowed
MTU values to be sure.

Jonathan Kollasch