Sets the maximum interval, in milliseconds (10-600000, default 3000), between IIH (hello) PDUs sent on multi-access (LAN) circuits at this level; on an L1L2 point-to-point circuit, the Level 1 value of this object is actually used for both levels' hello interval, and attempting to set a different value at Level 2 on such a circuit returns InconsistentValue. An admin lowers this to detect neighbor loss faster (combined with isisCircLevelHelloMultiplier's holding-time multiplier), understanding the L1/L2 sharing quirk on point-to-point circuits.