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 ~]$
===
Can this be made to work again?
Thanks.
Jay B.
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