4-O-[(D-ribitylphospho)(n)-di{(2R)-glycerylphospho}]-N-acetyl-beta-D-mannosaminyl-(1->4)-N-acetyl-alpha-D-glucosaminyl di-trans,octa-cis-undecaprenyl diphosphate + n UDP-N-acetyl-alpha-D-glucosamine = 4-O-([2-N-acetyl-beta-D-glucosaminyl-1-D-ribitylphospho](n)-di{[2R]-1-glycerylphospho})-N-acetyl-beta-D-mannosaminyl-(1->4)-N-acetyl-alpha-D-glucosaminyl di-trans,octa-cis-undecaprenyl diphosphate + n UDP + n H(+) — reaction