NON-STOP FORWARDING IN A MULTI-CHASSIS ROUTER

State information is synchronized between a plurality of routing engines in a multi-chassis router according to a synchronization gradient. An example multi-chassis router is described that includes a primary routing engine and a standby routing engine in each chassis. According to the synchronization gradient, the primary routing engine of a control node updates state information on the standby routing engine of the control node prior to updating the primary routing engines of the other chassis. The primary routing engines of the other chassis update state information in respective standby routing engines prior to updating state information in consumers. If a primary routing engine fails, the corresponding standby routing engine assumes control of the primary routing engine's duties. Upon assuming control, a standby routing engine resumes updating state information without having to resend state information or interrupt packet forwarding.