DMS-100 Family EIU User Guide TELECOM12185Appendix I: Obtaining a MAC addressThis appendix provides information on media access control (MAC)addresses1, and on obtaining a MAC address for the Ethernet interface unit(EIU).OverviewThe standard among manufacturers of Internetworking hardware is that theMAC address is hard-coded in read-only memory (ROM) on each device. Theaddress becomes a unique identifier, and this standard ensures that no twodevices have the same identifier.The EIU departs from this standard in that, while Nortel controls the MACaddress and the address is still unique, the operating company is responsiblefor recording this address in datafill. While there is flexibility in assigning theMAC address to EIU, this flexibility can cause problems if MAC addresses arenot unique across the network or the Internetwork. The operating companymust ensure that the datafilled address is correct, or addressing conflicts canoccur.Administrative personnel assign a unique MAC address to each EIU usingtable control datafill in table LIUINV.MAC address formatAs defined by IEEE Standard 802.3, a MAC address is either 16 or 48 bitslong. SuperNode supports 48-bit addresses. The 48-bit MAC address structureis shown in figure 47.1. The MAC address is also known as an Ethernet address. In this document, the industry -standard term MAC address is used.
