=head1 NAME

App::Netdisco::Manual::Troubleshooting - Tips and Tricks for Troubleshooting

=head1 Understanding Nodes and Devices

The two basic components in Netdisco's world are Nodes and Devices. Devices
are your network hardware, such as routers, switches, and firewalls. Nodes are
the end-stations connected to Devices, such as workstations, servers,
printers, and telephones.

Devices respond to SNMP, and therefore can report useful information about
themselves such as interfaces, operating system, IP addresses, as well as
knowledge of other systems via MAC address and ARP tables. Devices are
actively contacted by Netdisco during a discover (and other polling jobs such
as macsuck, arpnip).

Netdisco discovers Devices using "neighbor protocols" such as CDP and LLDP. We
assume your Devices are running these protocols and learning about their
connections to each other. If they aren't, you'll need to configure manual
topology within the web interface (or simply have standalone Devices).

Nodes, on the other hand, are passive as far as Netdisco is concerned. The
only job that contacts a Node is nbtstat, which makes NetBIOS queries. Nodes
are learned about via the MAC and ARP tables on upstream Devices.

Because Netdisco only learns about Devices through a neighbor protocol, it's
possible to run an SNMP agent on a Node. Only if the Node is also advertising
itself via a neighbor protocol will Netdisco treat it as a Device. This can
account for undesired behaviour, such as treating a server (Node) as a Device,
or vice versa only recognising a switch (Device) as a Node.

To prevent avoid discovery of any target as a Device, use the C<discover_no>,
C<discover_no_type>, or C<discover_only> configuration settings. If you don't
see links between Devices in Netdisco, it might be because they're not running
a neighbor protocol, or for some reason not reporting the relationships to
Netdisco. Use the C<show> command to troubleshoot this:

 ~netdisco/bin/netdisco-do show -d 192.0.2.1 -e c_id

=head1 Understanding Netdisco Jobs

Please read the section above, if you've not yet done so.

Netdisco has four principal job types:

=over 4

=item discover

Gather information about a Device, including interfaces, vlans, PoE status,
and chassis components (modules). Also learns about potential new Devices via
neighbor protocols and adds jobs for their discovery to the queue.

=item macsuck

Gather MAC to port mappings from known Devices reporting Layer 2 capability.
Wireless client information is also gathered from Devices supporting the
802.11 MIBs.

=item arpnip

Gather MAC to IP mappings from known Devices reporting layer 3 capability.

=item nbtstat

Poll a Node to obtain its NetBIOS name.

=back

The actions as named above will operate on one device only. Complimentary job
types C<discoverall>, C<macwalk>, C<arpwalk>, and C<nbtwalk> will enqueue one
corresponding single-device job for each known device. The Netdisco backend
daemon will then process the queue (in a random order).

=head1 Run a C<netdisco-do> Task with Debugging

The C<netdisco-do> command has several debug flags which will show what's
going on internally. Usually you always add C<-D> for general Netdisco
debugging, then C<-I> for L<SNMP::Info> logging and C<-Q> for SQL tracing. For
example:

 ~netdisco/bin/netdisco-do discover -d 192.0.2.1 -DIQ

You will see that SNMPv2 community strings are hidden by default, to make the
output safe for sending to Netdisco developers. To show the community string,
set the C<SHOW_COMMUNITY> environment variable:

 SHOW_COMMUNITY=1 ~netdisco/bin/netdisco-do discover -d 192.0.2.1 -DIQ

=head1 Dump an SNMP object for a Device

This is useful when trying to work out why some information isn't displaying
correctly (or at all) in Netdisco. It may be that the SNMP response isn't
understood. Netdisco can dump any leaf or table, by name:

 ~netdisco/bin/netdisco-do show -d 192.0.2.1 -e interfaces
 ~netdisco/bin/netdisco-do show -d 192.0.2.1 -e Layer2::HP::interfaces

You can combine this with SNMP::Info debugging, shown above (C<-I>).

=head1 Interactive SQL terminal on the Netdisco Database

Start an interactive terminal with the Netdisco PostgreSQL database. If you
pass an SQL statement in the "-e" option then it will be executed.

 ~netdisco/bin/netdisco-do psql
 ~netdisco/bin/netdisco-do psql -e 'SELECT ip, dns FROM device'
 ~netdisco/bin/netdisco-do psql -e 'COPY (SELECT ip, dns FROM device) TO STDOUT WITH CSV HEADER'

The last example above is useful for sending data to Netdisco developers, as
it's more compact and readable than the standard tabular output (second
example).

=head1 Database Schema Redeployment

The database schema can be fully redeployed (even over an existing
installation), in a safe way, using the following command:

 ~netdisco/bin/netdisco-db-deploy --redeploy-all

=head1 Debug HTTP Requests and Configuration

You can see HTTP Headers received by Netdisco, and other information such as
how it's parsing the config file, by enabling the Dancer debug plugin.  First
download the plugin:

 ~netdisco/bin/localenv cpanm --notest Dancer::Debug

Then run the web daemon with the environment variable to enable the feature:

 DANCER_DEBUG=1 ~/bin/netdisco-web restart

A side panel appears in the web page with debug information. Be sure to turn
this off when you're done (stop and start without the environment variable)
otherwise secrets could be leaked to end users.

=head1 Neighbor Relations on Juniper EX

The LLDP configuration should look like:

 lldp {
   management-address 10.0.0.1;
   port-id-subtype interface-name;
   interface all;
 }

=head1 Report Cisco 37xx as Single Device Instead of Stacked

Add this to your 37xx config:

 no snmp-server sysobjectid type stack-oid

=head1 Running under C<systemd>

On C<systemd>-based systems please see L<our Systemd
guide|App::Netdisco::Manual::Systemd>.

=cut
