Fault tolerant managed switching element architecture

A non-transitory machine readable medium storing a program for execution by at least one processing unit of a managed edge switching element (MESE) that connects to a plurality of managed non-edge switching elements (MNESEs) in a hierarchical switching architecture, the program for identifying a MNESE to which the MESE forwards a packet for further processing, the program comprising sets of instructions for:

• performing a hash function based on the packet to generate a hash value;
• identifying a record for a particular MNESE from a hierarchy traversal table by comparing the hash value against a range list that matches ranges of hash values to MNESEs, the record specifying a first physical MNESE as a primary MNESE and a second physical MNESE as a secondary MNESE for the particular MNESE, said MNESEs for receiving the packet from the MESE for processing when the MESE does not have a flow entry to forward the packet to a destination of the packet;
• determining whether the first physical MNESE specified by the record has failed;
• when the first physical MNESE has not failed, forwarding the packet to the first physical MNESE;
• and
• when the first physical MNESE has failed, forwarding the packet to the second physical MNESE.