With the extension of IPv6 IS-IS MT, the new type, length, and value (TLV) parameters are added into the IS to IS hello (IIH) packets that advertise the topologies of the interface. In IPv6 IS-IS MT, the router advertises its information using the new TLV parameters such as MT ID TLV, MT IS Reachability TLV, MT Reachable IPv4 TLV, and MT Reachable IPv6 TLV. The TLVs specify the types of data, the maximum length of the data, and the valid values for the data.