monitor monthly bandwidth interface of SNMP devices

[ab-tech]

Hello,
i use zabbix with my some server (with zabbix agent) and works fine.
i use zabbix also to monitor my network devices (SNMP) and works fine.
i can get network traffic of all interfaces (ex switch or router)

on some devices with LTE interface i would get total traffic of in/out for month.

i know about this is impossibile, given that i "update interval" traffic every 1minute.
but to have an estimate (10gb or 50gb just to have an idea), can i sum or trend every value saved in zabbix database?

i try to add a calculated item with formula (only for incoming traffic)
sum(/<host>/net.if.in[ifHCInOctets.3],30d)

but seems not corresponding to value on devices... (i can only view in realtime, but i can read it by SNMP value)

thank you in advance

[zerono]

any update?

[ab-tech]

no, i don't have a solution...

for now i check on my devices (hoping not reboot)...

i think can i create a script on mikrotik that send to zabbix a value then reset counter.
but how i can reset this value every month?

and i think this is a more complicated way.... there is no other way?
thank you