On 10 February 2011 21:49, Jay Borkenhagen <j...@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
> r...@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@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@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@cactus ~]$ uname -v
> FreeBSD 6.2-PRERELEASE #0: Tue Dec 26 16:53:18 EST 2006
> r...@cactus.iplabs.att.com:/usr/obj/usr/src/sys/CACTUS
> [jayb@cactus ~]$
>
> [jayb@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@cactus ~]$
>
> [jayb@cactus ~]$ sudo ifconfig em0 mtu 9000
> [jayb@cactus ~]$ ifconfig em0 | grep mtu
> em0: flags=8843<UP,BROADCAST,RUNNING,SIMPLEX,MULTICAST> mtu 9000
> [jayb@cactus ~]$
>
> [jayb@cactus ~]$ pciconf -lv | sed -n '/em0@/,/none0@/p'
> em0@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@pci0:4:0: class=0x088000 card=0x0767101e chip=0x9063101e rev=0x04
> hdr=0x00
> [jayb@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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