# Interface Description Parsing

Librenms can interpret, display and group certain additional information on ports.
This is done based on the format that the port description is written,
although it's possible  to customise the parser to be specific for your setup.

## Keywords

See [examples](#examples) for formats.

- **Keywords**
  - `Cust`    - Customer
  - `Transit` - Transit link
  - `Peering` - Peering link
  - `Core`    - Infrastructure link (non-customer)
- Info-keywords
  - `()` contains a note
  - `{}` contains *your* circuit id
  - `[]` contains the service type or speed

## Examples

Cisco IOS / NXOS / IOSXR:

```text
interface Gi0/1
descr Transit: Example Provider (AS65000)
interface Gi0/2
descr Peering: Peering Exchange
interface Gi0/3
descr Core: core.router01 FastEthernet0/0 (Telco X CCID023141)
interface Gi0/4
descr Cust: Example Customer [10Mbit] (T1 Telco Y CCID129031) {EXAMP0001}
```

Unix / Linux:

This requires an additional script to be [setup](#device-setup)

```text
# eth3: Cust: Example Customer [10Mbit] (T1 Telco Y CCID129031) {EXAMP0001}
# eth0: Transit: Example Provider (AS65000)
# eth1: Core: core.router01 FastEthernet0/0 (Telco X CCID023141)
# eth2: Peering: Peering Exchange
```

## Customisation

The following config options can be set to enable more custom types:

!!! setting "webui/port-descr"
    ```bash
    lnms config:set customers_descr.+ 'cust'
    lnms config:set transit_descr.+ 'transit'
    lnms config:set peering_descr.+ 'peering'";'
    lnms config:set core_descr.+ 'core'
    lnms config:set custom_descr.+ 'something_made_up'
    ```

## Custom interface parser

It's also possible to write your own parser, the existing one is: includes/port-descr-parser.inc.php

Once you've created your own then you can enable it with:

!!! setting "webui/port-descr"
    ```bash
    lnms config:set port_descr_parser includes/custom/my-port-descr-parser.inc.php
    ```

Here is an example of a very simple file that parses type and descr.
```php
<?php

return function (string $ifAlias): array {
    if (! str_contains(':', $ifAlias)) {
        return [];
    }

    $parts = explode(':', $ifAlias, 2);

    return [
        'type' => $parts[0],
        'descr' => $parts[1],
    ];
};
```

#### Fields

Fields you can fill in your returned array

 - type: port type (only defined types will show as graphs)
 - descr: description of the port
 - circuit: usually a circuit id
 - speed: can be a plan name or a numeric speed 10G (or asymmetric 10G/500M), numeric speeds
   can used by custom maps and some graphs
 - notes: notes

#### Variables

Variables you can request for your function include:

 - string $ifAlias
 - int $port_id
 - string $ifName
 - int $ifIndex
 - \App\Models\Device $device

### Device Setup

For Unix / Linux based systems, you need to run an additional script
to support the parsing of interface information.

- Add `ifAlias` from `/var/www/librenms/scripts/` or download it from
  [here](https://github.com/librenms/librenms/blob/master/scripts/ifAlias)
  to the Server and make it executable `chmod +x /path/to/ifAlias`
- Add to `snmpd.conf` something like:
    ``pass .1.3.6.1.2.1.31.1.1.1.18 /path/to/ifAlias``
- Add aliases with
  - `iproute2` package like:
    ``ip link set eth0.427 alias 'Cust: CustomerA'``
  - in `/etc/network/interfaces` or `/etc/network/interfaces.d/*` with a comment like:
    ``# eth0.427: Cust CustomerA``

- Restart `snmpd` - `systemctl restart snmpd`

There are no changes to be made or additions to install for the polling librenms.

Now you can set up your [keywords](#keywords) in your aliases.
