A conceptual row in the inetIcmpTable. A row with an inetIcmpIfIndex value of zero indicates a system-wide value; a row with a non-zero inetIcmpIfIndex indicates an interface-specific value. A system may provide both system-wide and interface-specific values, in which case it is important to note that the system-wide value may not be equal to the sum of the interface-specific value across all interfaces due to e.g. dynamic interface creation/deletion.