Logstash SNMP input plugin: no data extracted

Hi,

I am using the SNMP input plugin with the following configurations:

input {
  snmp {
    walk => ["1.3.6.1.2.1.1"]
    hosts => [{host => "udp:XXXXXXXX/161" community => "public" version => "2c"  retries => 2  timeout => 1000}]
  }
}
output{
  stdout { codec => "rubydebug"}
}

I haven't errors in the logstash log but no data is extracted, while putting a wrong ip I see errors in the log.
Can you help me to understand why no data are extracted?

Logstash version: 7.6.2

Thanks

Daniele