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Date:      Mon, 09 Sep 2013 15:02:22 +0200
From:      Marek Salwerowicz <marek_sal@wp.pl>
To:        freebsd-net@freebsd.org
Subject:   igb Intel Gigabit Network Connection I350, lagg, vlan - increase mtu
Message-ID:  <522DC6DE.3040908@wp.pl>
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Hi,

My server is running with 4 Gigabit NICs:

igb0@pci0:5:0:0:        class=0x020000 card=0x152115d9 chip=0x15218086 
rev=0x01 hdr=0x00
     vendor     = 'Intel Corporation'
     device     = 'I350 Gigabit Network Connection'
     class      = network
     subclass   = ethernet
igb1@pci0:5:0:1:        class=0x020000 card=0x152115d9 chip=0x15218086 
rev=0x01 hdr=0x00
     vendor     = 'Intel Corporation'
     device     = 'I350 Gigabit Network Connection'
     class      = network
     subclass   = ethernet
igb2@pci0:5:0:2:        class=0x020000 card=0x152115d9 chip=0x15218086 
rev=0x01 hdr=0x00
     vendor     = 'Intel Corporation'
     device     = 'I350 Gigabit Network Connection'
     class      = network
     subclass   = ethernet
igb3@pci0:5:0:3:        class=0x020000 card=0x152115d9 chip=0x15218086 
rev=0x01 hdr=0x00
     vendor     = 'Intel Corporation'
     device     = 'I350 Gigabit Network Connection'
     class      = network
     subclass   = ethernet


those NICs are connected to switch with LACP aggregation:

lagg0: 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 00:25:90:c1:1d:18
         inet6 fe80::225:90ff:fec1:1d18%lagg0 prefixlen 64 scopeid 0x8
         nd6 options=21<PERFORMNUD,AUTO_LINKLOCAL>
         media: Ethernet autoselect
         status: active
         laggproto lacp lagghash l2,l3,l4
         laggport: igb3 flags=1c<ACTIVE,COLLECTING,DISTRIBUTING>
         laggport: igb2 flags=1c<ACTIVE,COLLECTING,DISTRIBUTING>
         laggport: igb1 flags=1c<ACTIVE,COLLECTING,DISTRIBUTING>
         laggport: igb0 flags=1c<ACTIVE,COLLECTING,DISTRIBUTING>


Using this lagg interface I created 2 vlan interfaces:

vlan14: flags=8843<UP,BROADCAST,RUNNING,SIMPLEX,MULTICAST> metric 0 mtu 1500
         options=103<RXCSUM,TXCSUM,TSO4>
         ether 00:25:90:c1:1d:18
         inet 192.168.1.65 netmask 0xffffff00 broadcast 192.168.1.255
         inet6 fe80::225:90ff:fec1:1d18%vlan14 prefixlen 64 scopeid 0x9
         nd6 options=29<PERFORMNUD,IFDISABLED,AUTO_LINKLOCAL>
         media: Ethernet autoselect
         status: active
         vlan: 14 parent interface: lagg0


vlan900: flags=8843<UP,BROADCAST,RUNNING,SIMPLEX,MULTICAST> metric 0 mtu 
1500
         options=103<RXCSUM,TXCSUM,TSO4>
         ether 00:25:90:c1:1d:18
         inet6 fe80::225:90ff:fec1:1d18%vlan900 prefixlen 64 scopeid 0xa
         inet 172.25.25.65 netmask 0xffff0000 broadcast 172.25.255.255
         nd6 options=29<PERFORMNUD,IFDISABLED,AUTO_LINKLOCAL>
         media: Ethernet autoselect
         status: active
         vlan: 900 parent interface: lagg0


I would like to increase the MTU on cards, but I can't set it in any way:

% sudo ifconfig igbX mtu 9000 [14:59:37]
ifconfig: ioctl (set mtu): Invalid argument


event setting the MTU to 1500 (default value) results in same error.
same for lagg0, and vlanX


How can I increase the MTU for lagg interface ?
Is it possible without rebooting or only via /etc/rc.conf ?

Regards,
-- 
Marek Salwerowicz

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