One of these highways, the Eiscir Riada, extended from the declivity on which Dublin Castle now stands, to the peninsula of Marey, at the head of Galway Bay.

It divided Conn's half of Ireland from the half possessed by Eoghan Mor, with whom he lived in the usual state of internecine feud which characterized the reigns of this early period.
One of the principal quarrels between these monarchs, was caused by a complaint which Eoghan made of the shipping arrangements in Dublin.
Conn's half (the northern side) was preferred, and Eoghan demanded a fair division.

They had to decide their claims at the battle of Magh Lena.[102] Eoghan was assisted by a Spanish chief, whose sister he had married.

But the Iberian and his Celtic brother-in-law were both slain, and the mounds are still shown which cover their remains.
Conn was succeeded by Conaire II., the father of the three Cairbres, who were progenitors of important tribes.

Cairbre Muse gave his name to six districts in Munster; the territory of Corcabaiscinn, in Clare, was named after Cairbre Bascain; and the Dalriada of Antrim were descended from Cairbre Riada.