A third confederation, the most powerful in Gaul at this time, the Arvernians, who were rivals of the AEduans, gave their countenance to the Allobrogians.

The AEduans, with whom the Massilians had commercial dealings, solicited through these latter the assistance of Rome.

A treaty was easily concluded.

The AEduans obtained from the Romans the title of friends and allies; and the Romans received from the AEduans that of brothers, which amongst the Gauls implied a sacred tie.
The consul Domitius forthwith commanded the Allobrogians to respect the territory of the allies of Rome.

The Allobrogians rose up in arms and claimed the aid of the Arvernians.