This selects which of the eight stored 3xDES keys, or a random selection among them, or clear, meaning no encryption, this specific route uses when cdmipIpRoute3xDes is enabled. The random(9) option is notable because it means the route does not use a fixed, predictable key slot; instead the modem picks among the eight configured keys, which can complicate troubleshooting decryption failures on the receiving end since the actual key in use for the next packet is not deterministic from this object's value alone. Setting this to key3(3) ties this route's encryption specifically to whatever value is stored in cdmipTransmitKey3, so rotating that key slot alone, without touching this setting, changes the effective key used by this route.