cannot set mtu > 1500 on em0 optical Gig-E

[Jack Vogel]

Thanks Sergey :)

Jack


On Thu, Feb 10, 2011 at 12:28 PM, Sergey Kandaurov <pluknet at gmail.com>wrote:

> On 10 February 2011 21:49, Jay Borkenhagen <jayb at braeburn.org> wrote:
> > Hi,
> >
> > For quite a while now it appears that mtu on my gigabit ethernet fiber
> > em0 cards cannot be configured higher than the default 1500 bytes.
> >
> > Here's what I get when I attempt to set it lower and higher on a brand
> > new 8.2-RC3 box:
> >
> > ===
> > sandbox# uname -v
> > FreeBSD 8.2-RC3 #0: Sun Jan 30 06:52:51 UTC 2011
> root at almeida.cse.buffalo.edu:/usr/obj/usr/src/sys/GENERIC
> > sandbox#
> >
> > sandbox# ifconfig em0
> > em0: flags=8843<UP,BROADCAST,RUNNING,SIMPLEX,MULTICAST> metric 0 mtu 1500
> >     options=18<VLAN_MTU,VLAN_HWTAGGING>
> >     ether 00:d0:b7:7c:f8:01
> >     inet 10.1.2.3 netmask 0xffffff00 broadcast 10.1.2.255
> >     media: Ethernet autoselect
> >     status: no carrier
> > sandbox# ifconfig em0 mtu 1499
> > sandbox# ifconfig em0 | grep mtu
> > em0: flags=8843<UP,BROADCAST,RUNNING,SIMPLEX,MULTICAST> metric 0 mtu 1499
> > sandbox# ifconfig em0 mtu 1501
> > ifconfig: ioctl (set mtu): Invalid argument
> > sandbox# ifconfig em0 | grep mtu
> > em0: flags=8843<UP,BROADCAST,RUNNING,SIMPLEX,MULTICAST> metric 0 mtu 1499
> > sandbox# ifconfig em0 mtu 1500
> > sandbox# ifconfig em0 | grep mtu
> > em0: flags=8843<UP,BROADCAST,RUNNING,SIMPLEX,MULTICAST> metric 0 mtu 1500
> > sandbox#
> >
> > sandbox# pciconf -lv | sed -n '/em0@/,/em1/p'
> > em0 at pci0:0:2:0:  class=0x020000 card=0x10008086 chip=0x10008086 rev=0x03
> hdr=0x00
> >    vendor     = 'Intel Corporation'
> >    device     = '82542 Gigabit Ethernet Controller'
> >    class      = network
> >    subclass   = ethernet
> > em1 at pci0:0:4:0:  class=0x020000 card=0x10008086 chip=0x10008086 rev=0x03
> hdr=0x00
> > sandbox#
> >
> > ===
> >
> > However, back in the 6.2 days it allowed it:
> >
> > ===
> >
> > [jayb at cactus ~]$ uname -v
> > FreeBSD 6.2-PRERELEASE #0: Tue Dec 26 16:53:18 EST 2006
> root at cactus.iplabs.att.com:/usr/obj/usr/src/sys/CACTUS
> > [jayb at cactus ~]$
> >
> > [jayb at cactus ~]$ ifconfig em0
> > em0: flags=8843<UP,BROADCAST,RUNNING,SIMPLEX,MULTICAST> mtu 1500
> >     options=8<VLAN_MTU>
> >     inet 10.0.1.152 netmask 0xfffffffc broadcast 10.0.1.155
> >     ether 00:90:27:e3:0a:67
> >     media: Ethernet autoselect
> >     status: no carrier
> > [jayb at cactus ~]$
> >
> > [jayb at cactus ~]$ sudo ifconfig em0 mtu 9000
> > [jayb at cactus ~]$ ifconfig em0 | grep mtu
> > em0: flags=8843<UP,BROADCAST,RUNNING,SIMPLEX,MULTICAST> mtu 9000
> > [jayb at cactus ~]$
> >
> > [jayb at cactus ~]$ pciconf -lv | sed -n '/em0@/,/none0@/p'
> > em0 at pci0:2:0:    class=0x020000 card=0x10008086 chip=0x10008086 rev=0x02
> hdr=0x00
> >    vendor   = 'Intel Corporation'
> >    device   = '82542 Gigabit Ethernet Controller'
> >    class    = network
> >    subclass = ethernet
> > none0 at pci0:4:0: class=0x088000 card=0x0767101e chip=0x9063101e rev=0x04
> hdr=0x00
> > [jayb at cactus ~]$
> >
>
> Hmm.. Did jumbo frames really work on these cards for you? Intel claims:
> "Adapters based on the Intel® 82542 and 82573V/E controller do not
> support Jumbo Frames. These correspond to the following product names:
>
>    * Intel® PRO/1000 Gigabit Server Adapter
>    * Intel® PRO/1000 PM Network Connection "
>
> As seen from code, the behavior was changed to match the description ("keep
> old 82542 from using jumbo frames") and merged to 6-STABLE before 6.3.
>
> --
> wbr,
> pluknet
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