Are there any guidelines in regards to the use of Special Characters in the SNMPv1 or SNMPv2c Community String for Spectrum?
RFC1157 (SNMPv2) and RFC1901 (SNMPv2c) does not provide any guidance or restrictions for the use of Special Characters used in the SNMP Community String. Therefore the list of allowed, or prohibited Special Characters could vary between vendors, and in some cases even between product lines for the same vendor. It's recommended to always check with the manufacturer of the device if you have questions regarding the use of Special Characters in the SNMP community strings.
In general you should avoid using any special characters reserved for functions by the operating system. For example, the "@" character is reserved by the Cisco IOS for SNMP indexing (VLAN Designation), and is known to cause problems for some of the Cisco product lines.
Likewise, Spectrum also uses the "@" character for querying instances of data, similar to the way Some Cisco IOS and F5 Operation Systems do. A good example would be when querying a VLAN from MIB Tools. To walk a particular VLAN, you would enter the "community_name@VLAN" in the SNMP Community String field.
If you use the "@" character in the SNMP Community Sting you run the risk of the device, or even the Network Management System, getting confused on what it is you are wanting to poll. Therefore the use of the "@" character in the SNMP Community String is not recommended.
Special Character used by Spectrum that are not recommended to be used in an SNMP Community String are:
For more regarding Cisco SNMP Community String Indexing
For a list of restricted Special Characters for F5 BigIP devices see SOL6449: Using special Characters in SNMP community strings.