Scalability of Ethernet is a known issue where communication is disturbed by broadcast traffic caused by a large number of nodes in a single broadcast domain. This paper proposes Extensible Transparent Filter (ETF) for Ethernet using SDN, that suppresses broadcast traffic in a broadcast domain by selecting an appropriate outgoing port of the switch through which the target host of broadcast packet is reachable. ETF maintains both consistent functionality and backward compatibility of the existing networking protocols such as Address Resolution Protocol, Dynamic Host Configuration Protocol, and other possible protocols that work with the broadcast of a packet. ETF was developed using Trema and Floodlight, which are open source SDN controller supporting OpenFlow. The number of flooding was significantly reduced in a broadcast domain where user clients connecting to the same VLAN across multiple production SDN switches successfully performed DHCP and ARP respectively. This paper also discusses the practical deployment and operation of SDN and ETF as a part of campus network in Indian Institute of Technology Hyderabad. The proposed approach improves scalability of a broadcast domain of Ethernet as an enhancement to the existing enterprise networks using SDN. © 2014 IEEE.