Network connections are lost from time to time

[Julian Elischer]

On 4/19/13 5:54 PM, C. L. Martinez wrote:
> On Fri, Apr 19, 2013 at 9:22 AM, C. L. Martinez <carlopmart at gmail.com>wrote:
>
>>
>>
>> On Fri, Apr 19, 2013 at 7:11 AM, C. L. Martinez <carlopmart at gmail.com>wrote:
>>
>>> 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??
>>>
>> More info when I try to connect with PuTTY from a windows desktop appears
>> the following error:
>>
>> Network error: Software caused connection abort.
>>
>>   ... and pf is disabled (ipfw and ipfilter, too).
>>
>>
> More info: I have intermittent failures with sendmail:
>
>                  /var/spool/mqueue (1 request)
> -----Q-ID----- --Size-- -----Q-Time-----
> ------------Sender/Recipient-----------
> r3J9o54G022686      243 Fri Apr 19 09:50 <root at domain.com>
>                   (reply: read error from [10.196.0.100])
>                                           susor1 at domain.com
>                  Total requests: 1
>
> It is really strange ...

are you sure you do not have another virtual machine with the same 
address? (LL or IP)


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