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Date:      Mon, 25 May 2015 09:59:45 +0200
From:      "Mark Schouten" <mark@tuxis.nl>
To:        Cs <bimmer@field.hu>
Cc:        "freebsd-net@freebsd.org" <freebsd-net@freebsd.org>
Subject:   Re: FreeBSD 10.1-REL - network unaccessible after high traffic
Message-ID:  <13CD4CDB-1744-4E2F-8FD7-BFE2365121F3@tuxis.nl>
In-Reply-To: <5562D0F3.4070408@field.hu>
References:  <5562D0F3.4070408@field.hu>

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Try lowering your mtu to 1500, that worked miracles for me..

--=20
Mark Schouten
Tuxis Internet Engineering
mark@tuxis.nl / 0318 200208

> On 25 May 2015, at 09:36, "Cs" <bimmer@field.hu> wrote:
>=20
> Hi all,
>=20
> I have two FreeBSd 10.1-RELEASE servers connected to each other. They were=
 connected via cross link, but they are connected to a cisco switch now (the=
 problem was the same with cross link too). When transferring huge files (50=
-500GB backup files) via Gigabit (it is important!) the network randomly die=
s. The backup runs every day/week and sometimes the connection is ok for mon=
ths sometimes it happens twice a week. When the network dies I can log in to=
 the server via IPMI and use the console everything is OK, but can't send an=
ything out on the network. ifconfig em0 down/up doesn't help nor netif resta=
rt. The problem never occured when I used 100Mbit connection between them, b=
ut it was 3com NIC (xl), gigabit adapter is Intel (em0). When I limit the tr=
ansfer rate (rsync bandwith limit or ipfw pipe) the problem is much more rar=
e.
>=20
> I tried to set these tuning parameters on both servers with different buff=
er size but nothing helped:
>=20
> # cat /etc/sysctl.conf
> security.bsd.see_other_uids=3D0
> net.inet.tcp.recvspace=3D512000
> net.route.netisr_maxqlen=3D2048
> kern.ipc.nmbclusters=3D1310720
> net.inet.tcp.sendbuf_max=3D16777216
> net.inet.tcp.recvbuf_max=3D16777216
> kern.ipc.soacceptqueue=3D32768
>=20
> # cat /boot/loader.conf
> geom_mirror_load=3D"YES" # RAID1 disk driver (see gmirror(8))
> ipfw_load=3D"YES"
> net.inet.ip.fw.default_to_accept=3D1
> kern.maxusers=3D4096
> accf_data_load=3D"YES"
>=20
> The duplex settings are identical on both servers.
>=20
> Server A:
> em1: flags=3D8843<UP,BROADCAST,RUNNING,SIMPLEX,MULTICAST> metric 0 mtu 900=
0
> options=3D4219b<RXCSUM,TXCSUM,VLAN_MTU,VLAN_HWTAGGING,VLAN_HWCSUM,TSO4,WOL=
_MAGIC,VLAN_HWTSO>=20
>        ether 00:25:90:24:52:66
>        inet x.x.x.x netmask 0xfffffe00 broadcast x.x.x.x
>        nd6 options=3D29<PERFORMNUD,IFDISABLED,AUTO_LINKLOCAL>
>        media: Ethernet autoselect (1000baseT <full-duplex>)
>        status: active
>=20
> Server B:
> em0: flags=3D8843<UP,BROADCAST,RUNNING,SIMPLEX,MULTICAST> metric 0 mtu 900=
0
> options=3D4219b<RXCSUM,TXCSUM,VLAN_MTU,VLAN_HWTAGGING,VLAN_HWCSUM,TSO4,WOL=
_MAGIC,VLAN_HWTSO>=20
>        ether 00:30:48:dd:fe:3e
>        inet x.x.x.x netmask 0xfffffe00 broadcast x.x.x.x
>        nd6 options=3D29<PERFORMNUD,IFDISABLED,AUTO_LINKLOCAL>
>        media: Ethernet autoselect (1000baseT <full-duplex>)
>        status: active
>=20
> Today I tried to set mtu to 9000 but in tcpdump I see that during scp it i=
s still 1500:
>    x.x.x.x.222 > x.x.x.x.37612: Flags [.], cksum 0xb6ee (incorrect -> 0xda=
6f), seq 35749, ack 113701596, win 7986, options [nop,nop,TS val 3103966325 e=
cr 853712893], length 0
> 09:27:33.912354 IP (tos 0x8, ttl 64, id 1028, offset 0, flags [DF], proto T=
CP (6), length 1500)
> 09:27:33.912358 IP (tos 0x8, ttl 64, id 1029, offset 0, flags [DF], proto T=
CP (6), length 1500)
>=20
>=20
> Any ideas? Thanks guys!
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