Beware the use of @ in SNMP Community Strings
Despite 25 years of working in IT, there are always things you come across late in the day and realize you have seen this issue before without understanding it correctly...
In a recent conversation with a Cisco engineer he pointed me to a reference online about the meaning of the “@” symbol in SNMP V1&2 community strings. Basically it has special meaning and is used to reference MIBs associated with specific instances. So for example PUBLIC@25 is read by Cisco devices as community string PUBLIC for VLAN 25.
A bit more research also found references to some switches only returning information for VLAN1 because the “@” symbol was being used and the switch was off looking for instances that don’t exist. An example might be the use of a community string such as Goaw@y123!. Cisco would read this a community string Goaw for interface “y123!” which clearly doesn’t exist.
The Cisco article doesn’t mention any other symbol with special meaning, so if you want to keep the mixture of letters numbers and characters, just swap the @ for something else!