Network connections are lost from time to time

[C. L. Martinez]

Hi all,

 I have a strange problem with my FreeBSD 9.1 (fully patched): I loose ssh
sessions from time to time frequently.

 This fbsd box is installed in an ESXi 5.1 server and I have another three
fbsd 9.1 in the same ESXi host that do not have this problem, but maybe the
problem is with my sysctl.conf and loader.conf settings:

sysctl.conf

# $FreeBSD: release/9.1.0/etc/sysctl.conf 112200 2003-03-13 18:43:50Z mux $
#
#  This file is read when going to multi-user and its contents piped thru
#  ``sysctl'' to adjust kernel values.  ``man 5 sysctl.conf'' for details.
#

# Uncomment this to prevent users from seeing information about processes
that
# are being run under another UID.
security.bsd.see_other_uids=0
security.bsd.see_other_gids=0

# Refresh arp table entries in 2 minutes
net.link.ether.inet.max_age=120

# Drop tcp/udp packets destined for closed ports
net.inet.tcp.blackhole=2
net.inet.udp.blackhole=1

# Use the H-TCP congestion control algorithm which is more aggressive
##net.inet.tcp.cc.algorithm=htcp

# Host cache is used to cache connection details and metrics
##net.inet.tcp.hostcache.expire=5400

# Maximum segment size (MSS) specifies the largest amount of data in a
single TCP segment
net.inet.tcp.mssdflt=1440

# Make sure time stamps are enabled for slowstart_flightsize
net.inet.tcp.rfc1323=1

# Make sure rfc3390 is DISABLED so the slowstart flightsize values are used.
net.inet.tcp.rfc3390=0

# Size of the TCP transmit and receive buffer.
net.inet.tcp.sendspace=262144

# Increase auto-tuning TCP step size of the TCP transmit and receive
buffers.
net.inet.tcp.recvbuf_inc=524288

# Somaxconn is the buffer or backlog queue depth for accepting new TCP
connections.
kern.ipc.somaxconn=1024

# Reduce the amount of SYN/ACKs we will _retransmit_ to an unresponsive
initial connection.
net.inet.tcp.syncache.rexmtlimit=1

# Spoofed packet attacks may be used to overload the kernel route cache.
net.inet.ip.rtexpire=60
net.inet.ip.rtminexpire=2
net.inet.ip.rtmaxcache=1024

loader.conf:

##############################################################
###  Loader settings  ########################################
##############################################################

autoboot_delay="5"
beastie_disable="YES"


##############################################################
###  Kernel tunables  ########################################
##############################################################

kern.maxfiles="25000"
kern.ipc.nmbclusters="32768"
net.inet.tcp.syncache.hashsize="1024"
net.inet.tcp.syncache.bucketlimit="100"
net.inet.tcp.tcbhashsize="4096"


##############################################################
###  Hardware tunables  ######################################
##############################################################

hw.pci.enable_msi="0"
hw.pci.enable_msix="0"


##############################################################
###  Networking modules  #####################################
##############################################################

cc_htcp_load="YES"


##############################################################
###  Other modules  ##########################################
##############################################################

aio_load="YES"

How can I debug where is the problem??