The knight is a class from the Player's Handbook II by Wizards of the Coast. Knights are dedicated melee combatants based around protecting other characters, distracting enemies, and high resilience. Their main ability is the "Knight's Challenge," which can boost the morale of allies, goad strong enemies into fighting him or her, and scare weak enemies. Knights must be of lawful alignment and maintain a specific code of conduct.
In Eberron, knights would tend to be from the upper classes, perhaps even bearing the noble ir' prefix to their name. The could be from any of the Five Nations. However, they would be unlikely to hail from Xen'drik, Lhazaar Principalities, Mror Holds, Darguun, Droaam, Shadow Marches, Eldeen Reaches or the Demon Wastes.