Advertising with a layer three routing protocol constituent link attributes of a layer two bundle

In general, techniques are described for extending routing protocol advertisements to include respective attributes of constituent links of an aggregation group. In one example, a network device includes a management interface that receives configuration information that specifies first and second constituent links for a layer two (L2) aggregated interface. The first and second constituent links are physical links connected to respective physical interfaces of forwarding units of the network device. A routing protocol daemon of the control unit generates a link state message that specifies layer three (L3) routing information associated with the aggregated interface and further specifies an attribute of the first constituent link and an attribute of the second constituent link. The routing protocol daemon sends the link state message from the network device to another network device of the network in accordance with a routing protocol.