# FreeBSD 10.1 - network unaccessible after high traffic



## banhalmi (May 23, 2015)

Hi,

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. When transferring huge files (50-500GB backup files) via Gigabit (it is important!) the network randomly dies. The backup runs every day/week and sometimes the connection is OK for months 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 anything out on the network. `ifconfig em0 down/up` doesn't help nor `service netif restart`. The problem never occurred when I used 100Mbit connection between them, but it was 3com NIC (xl), gigabit adapter is Intel (em0). When I limit the transfer rate (rsync bandwith limit) the problem is much more rare.

I tried to set these tuning parameters on both servers with different buffer size but nothing helped:

```
# cat /etc/sysctl.conf
security.bsd.see_other_uids=0
net.inet.tcp.recvspace=512000
net.route.netisr_maxqlen=2048
kern.ipc.nmbclusters=1310720
net.inet.tcp.sendbuf_max=16777216
net.inet.tcp.recvbuf_max=16777216
kern.ipc.soacceptqueue=32768

# cat /boot/loader.conf
geom_mirror_load="YES" # RAID1 disk driver (see gmirror(8))
ipfw_load="YES"
net.inet.ip.fw.default_to_accept=1
kern.maxusers=4096
accf_data_load="YES"
```
Any ideas? Thanks guys!


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## shurik (Jun 3, 2015)

There is a problem with em(4) driver in 10.1. Try to disable tso4.

https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=200221


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## SirDice (Jun 3, 2015)

Did you enable Jumbo frames? I have a bunch of em(4) cards that appear to lose their network connection after a while when the MTU is set to anything above 1500. A simple `ifconfig em0 down && ifconfig em0 up` fixes it but it's rather annoying. Using MTU 1500 there's no problems.


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