Add not about RFC3164 to syslog input readme

plugins/inputs/syslog/README.md

@@ -55,25 +55,7 @@ The [`best_effort`](https:/influxdata/go-syslog#best-effort-mode)
 option instructs the parser to extract partial but valid info from syslog
 messages. If unset only full messages will be collected.
 
-### Metrics
-
-- syslog
- - tags
- - severity (string)
- - facility (string)
- - hostname (string)
- - appname (string)
- - fields
- - version (integer)
- - severity_code (integer)
- - facility_code (integer)
- - timestamp (integer)
- - procid (string)
- - msgid (string)
- - sdid (bool)
- - *Structured Data* (string)
-
-### Rsyslog Integration
+#### Rsyslog Integration
 
 Rsyslog can be configured to forward logging messages to Telegraf by configuring
 [remote logging](https://www.rsyslog.com/doc/v8-stable/configuration/actions.html#remote-machine).
@@ -96,3 +78,31 @@ $ActionQueueSaveOnShutdown on # save in-memory data if rsyslog shuts down
 ```
 
 To complete TLS setup please refer to [rsyslog docs](https://www.rsyslog.com/doc/v8-stable/tutorials/tls.html).
+
+### Metrics
+
+- syslog
+ - tags
+ - severity (string)
+ - facility (string)
+ - hostname (string)
+ - appname (string)
+ - fields
+ - version (integer)
+ - severity_code (integer)
+ - facility_code (integer)
+ - timestamp (integer)
+ - procid (string)
+ - msgid (string)
+ - sdid (bool)
+ - *Structured Data* (string)
+
+
+### Troubleshooting
+
+The syslog plugin does not yet support RFC3164 format data. You may see the following error when this syslog format is received:
+``
+E! Error in plugin [inputs.syslog]: expecting a version value in the range 1-999 [col 5]
+```
+
+You can use rsyslog to translate RFC3164 syslog messages to RFC5424 or RFC5425 format.