Date: Fri, 13 Jan 2012 12:22:41 -0500 From: Iordan Iordanov <iordan@cdf.toronto.edu> To: freebsd-bugs@freebsd.org Cc: CDF Admin <admin@cdf.toronto.edu> Subject: unable to set mtu 9000 on Intel x520-t2 adapter Message-ID: <4F106861.80507@cdf.toronto.edu>
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Hello,
We are testing FreeBSD 9.0-RELEASE on a pair of machines with 10GBASE-T
Intel x520-t2 adapters interconnected with a straight-through cat6 rj45
cable. With mtu 1500, we are achieving aproximately 4 gigabits/s both
directions as demonstrated with iperf. We wanted to test with mtu 9000
to see whether there would be any difference, but we encountered a
problem setting it. We ran the following commands to alter the MTU to
9000 on the two machines (fw3 and fw4):
fw3# ifconfig ix1 192.168.1.100 mtu 9000
fw4# ifconfig ix1 192.168.1.200 mtu 9000
However, instead of getting mtu set to 9000, what we see is the
following message in the kernel output of both machines:
ix1: Could not setup receive structures
ix1: Could not setup receive structures
and no traffic getting through. The moment we run:
fw3# ifconfig ix1 192.168.1.100 mtu 1500
fw4# ifconfig ix1 192.168.1.200 mtu 1500
we see:
ix1: link state changed to DOWN
ix1: link state changed to UP
and traffic starts getting through as before. More information about our
hardware is:
Motherboard: Supermicro H8DGU-F
CPU: AMD 6128 8-core
Memory: 16GB DDR3
NICs: Intel x520-t2 10GbaseT adapters
An ifconfig ix1 output for one of the machines:
fw4# ifconfig ix1
ix1: flags=8843<UP,BROADCAST,RUNNING,SIMPLEX,MULTICAST> metric 0 mtu 1500
options=401bb<RXCSUM,TXCSUM,VLAN_MTU,VLAN_HWTAGGING,JUMBO_MTU,VLAN_HWCSUM,TSO4,VLAN_HWTSO>
ether 00:1b:21:d6:19:51
inet 192.168.1.200 netmask 0xffffff00 broadcast 192.168.1.255
nd6 options=29<PERFORMNUD,IFDISABLED,AUTO_LINKLOCAL>
media: Ethernet autoselect (autoselect <full-duplex>)
status: active
Many thanks for any help/action on this!
Sincerely,
Iordan Iordanov
CDF System Administrator
University of Toronto
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