There is no response (no error, no timeout) when querying SNMP 64-bit (High-Capacity) counters on VSX.

Example:

[Expert@VSX:0]# snmpwalk -n ctxname_vsid1 -v 3 -l authNoPriv -u <username> -A <password> localhost ifHCInOctets
[Expert@VSX:0]#

Affected environments:

1. VSX R77, VSX R77.10, VSX R77.20 that was upgraded using in-place upgrade
2. SNMP mode was configured to "vs" (Clish command 'set snmp mode vs') before the in-place upgrade