Strabo 4,6,8-9
'8 Next, in order, come those parts of the mountains that are towards the east, and those that bend round towards the south: the Rhaeti and the Vindelici occupy them, and their territories join those of the Elvetii and the Boii; for their territories overlook the plains of those peoples. Now the Rhaeti reach down as far as that part of Italy which is above Verona and Comum (moreover, the "Rhaetic" wine, which has the repute of not being inferior to the approved wines of the Italic regions, is made in the foot-hills of the Rhaetic Alps), and also extend as far as the districts through which the Rhenus runs; the Lepontii, also, and Camuni, belong to this stock. But the Vindelici and Norici occupy the greater part of the outer side of the mountain, along with the Breuni and the Genauni, the two peoples last named being Illyrians.198 All these peoples used to overrun, from time to time, the neighbouring parts, not only of Italy,
but also of the country of the Elvetii, the Sequani, the Boii and the Germans. The Licattii, the Clautenatii, and the Vennones proved to be the boldest warriors of all the Vindelici, as did the Rucantii and the Cotuantii of all the Rhaeti. The Estiones, also, belong to the Vindelici, and so do the Brigantii, and their cities, Brigantium and Cambodunum, and p283also Damasia, the acropolis, as it were, of the Licatii. The stories of the severity of these brigands towards the Italiotes are to this effect: When they capture a village or city, they not only murder all males from youths up but they also go on and kill the male infants, and they do not stop there either, but also kill all the pregnant women who their seers say are pregnant with male children.
9 Directly after these people come the peoples that dwell near the recess of the Adriatic and the districts round about Aquileia, namely, the Carni as well as certain of the Norici; the Taurisci,
also, belong to the Norici. But Tiberius and his brother Drusus stopped all of them from their riotous incursions by means of a single summer-campaign; so that now for thirty-three years they have been in a state of tranquillity and have been paying their tributes regularly.'
So, before the Romans pacified the region, the Rhaeti, the Vindelici, the Norici and the Illyrians used to overrun the Helvetii, the Sequani, the Boii and the Germans.
The Sequani?
*****GK: My take is that Strabo is compressing his info and that "all" means "each with respective neighbours". And geography gives you an initial indication as to "who against who". Falconer interprets "Sequani" as "the people of Franche Comte" : cf. "All these people were continually making incursions both into the neighbouring parts of Italy, and into [the countries] of the Helvetii, the Sequani,
2 the Boii, and the Germans." at