A network interface includes N input lanes that receive data symbols and idle symbols. A substitutor module periodically replaces an idle symbol on each input lane with a corresponding alignment symbol to form an alignment group. M interleaver modules each interleave a portion of the data symbols and alignment symbols onto a corresponding transmit lane based on an interleaving pattern that provides each transmit lane with N/M alignment symbols from the alignment group. M is an integer greater than 1 and N is greater than M. In some features the substitutor module periodically replaces successive idle symbols on each lane with alignment symbols to form corresponding alignment groups. An interleaver module interleaves the data symbols and alignment groups onto M transmit lanes according to an interleaving pattern that provides each transmit lane with one of the alignment groups.