Troubleshooting
===============

Logging into the SPIDR4
-----------------------

Please note that logging into the SPIDR4 is not encouraged. For daily use it should not be required. You can request the root password from the SPIDR4 team.
(Alternatively use username *spidr4*, password *medipix*).

I'm getting `Unable to negotiate with <IP address> port 22: no matching host key type found. Their offer: ssh-rsa`
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
For newer Linux versions RSA is disabled by default. Edit ``/etc/ssh/ssh_config``

You should see something like:

.. code:: 

    Include /etc/ssh/ssh_config.d/*.conf

    Host *
    #   ForwardAgent no
    #   ForwardX11 no
    #   ... and some more of this

At the end append the following:

.. code::

    HostKeyAlgorithms +ssh-rsa
    PubkeyAcceptedKeyTypes +ssh-rsa

And make sure it is indented.
Now it should allow you to get a login prompt (and also allow public/private key authentication).


10GbE not receiving packets or high losses
------------------------------------------

When running the example scripts (tpx4_xgbe_testpulse_*) or any other data acquisition over 10GbE but you are not receiving them in the data-acquisition application. First you need to know whether the packets are indeed received, but not forwarded to the application.

You can use ``tcpdump`` or ``wireshark`` to see if you are receiving the packets on your system. 

They are also not visible in wireshark/tcpdump
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

Most common issues are:
 - Older firmware
 - Bad network interface
 - SFP is not plugged into the right cage

Older firmware
""""""""""""""
Update the SPIDR4 system using the **spidr4mgr** tool.  

Bad network interface
"""""""""""""""""""""
Some SFP direct copper interfaces don't seem to work. Please only use actual optical SFP transceivers.

SFP is not plugged into the right cage
""""""""""""""""""""""""""""""""""""""
Make sure the SFP module is plugged in to the SFP cage closest to the power connector.


They are visible in wireshark/tcpdump
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

Most common issues are:
 - Incorrectly configured MTU
 - Firewall problems
 - Incorrect subnet

MTU problem
"""""""""""
The SPIDR4 sends so-called 'jumbo' frames, which are a little less than 9000 bytes in size. By default Ethernet frames of size larger than 1500 bytes are not accepted by a network interface, so you must configure your network interface to accept frames up to size 9000, by configuring the Maximum Transmission Unit (MTU).

*For Linux*
Check your MTU using IP:

.. code::

    ip link show dev <interface name>

And to set it to 9000:

.. code::

    sudo ip link set mtu 9000 dev <interface name>


Firewall issue
""""""""""""""

*For Linux*
When using ``firewalld``. Put your 10GbE network interface in the trusted zone:

.. code::

    sudo firewall-cmd --permanent --zone=trusted --change-interface=<interface name>



I am receiving packets, just not all of them
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

Please first check whether this is not an MTU issue. See section `MTU problem`. 

The SPIDR4 uses UDP, meaning there is no delivery guarantee.
Packet loss may occur:

- When using a slow (scripting) programming language.
- The system is busy doing other stuff.

Please use a compiled language for fast data processing, and make sure your system is not busy doing other things.