Thanks guys

Not sure why this would be happening on this system as I have much busier ones 
that are fine but I will have a look next time it happens.

Regards
Michael Knill

On 7/10/20, 12:23 pm, "Lonnie Abelbeck" <li...@lonnie.abelbeck.com> wrote:

    Thanks Darrick,

    If you have a very busy (network) system, you can set in your user.conf
    --
    CONNTRACK=65536
    --
    or some higher power of 2 ... that will survive a reboot.  Though higher 
values will use more RAM.

    BTW, CONNTRACK is a firewall variable.

    Lonnie




    > On Oct 6, 2020, at 7:19 PM, darricklegacy <dhart...@djhsolutions.com> 
wrote:
    > 
    > Hi Michael,
    > 
    > I have seen this error on our system from time to time.  If you are on a 
relatively busy network, you could exceed the 16384 value potentially. You can 
echo a larger value to that setting in /proc/sys/net but it will not survive a 
reboot. 
    > 
    > If you have a relatively small network, Lonnie is on the right track (pun 
intented).  You can check what's in the table by parsing /proc/net and looking 
at ip_conntrack.
    > 
    > Darrick
    > 
    > On 10/6/20, 5:38 PM, "Lonnie Abelbeck" <li...@lonnie.abelbeck.com> wrote:
    > 
    >    Hi Michael,
    > 
    >    I have never personally witnessed this error, but I am aware it can 
happen if the conntrack state table is full.
    > 
    >    By default CONNTRACK=16384 which sets the conntrack state table size.
    > 
    >    View the number states:
    >    System tab -> Firewall States
    >    --
    > 
    >    NNN Total Firewall States
    >    --
    > 
    >    Look to see what public TCP or UDP ports are exposed and see if 
someone might be probing them.
    > 
    >    Possibly you have a BitTorrent running internally ?  That can create a 
lot of states.
    > 
    >    If you really have a super busy system there is some tuning you can 
do, but I would look to see if you have some publicly exposed ports that can be 
firewalled better.
    > 
    >    Lonnie
    > 
    > 
    > 
    > 
    > 
    >> On Oct 6, 2020, at 4:50 PM, Michael Knill 
<michael.kn...@ipcsolutions.com.au> wrote:
    >> 
    >> Hi Group
    >> 
    >> For the second morning in a row, my office system has been pretty much 
unusable with the following in the logs:
    >> 
    >> user.warn kernel: nf_conntrack: table full, dropping packet
    >> 
    >> Is this a DoS attack? 
    >> Things are fine once rebooted. Surely this wouldn't be the case with a 
DoS attack?
    >> 
    >> Where should I test next?
    >> 
    >> Thanks all.  
    >> 
    >> Regards
    > 
    > 
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