This is a part of my snmpd,conf file (on the proxmox host):
###########################################################################
#SECTION: Access Control Setup
#This section defines who is allowed to talk to your running
#snmp agent.
#Views
#arguments viewname included [oid]
#system + hrSystem groups only
#view systemonly included .1.3.6.1.2.1.1
#view systemonly included .1.3.6.1.2.1.25.1
view systemonly included .1
#rocommunity: a SNMPv1/SNMPv2c read-only access community name
#arguments: community [default|hostname|network/bits] [oid | -V view]
#Read-only access to everyone to the systemonly view
rocommunity public default -V systemonly
rocommunity6 public default -V systemonly
…
In the default installation these rules are enabled:
view systemonly included .1.3.6.1.2.1.1
view systemonly included .1.3.6.1.2.1.25.1
Which limits the access to the two MIB Subtrees - they not include the one needed for the extensions
I replaced them with:
view systemonly included .1
which gives full read access to the complete MIB tree.