2-8 SmartSwitch ATM User GuideCreating an Emulated LAN IP Over ATM and LANEThe LECS address is constructed from:netprefix + chassis MAC address + selector byte of 01For examplenetprefix = 39:00:00:00:00:00:00:00:00:00:A3:87:0Bchassis MAC address = 00:00:1D:A3:87:0Bthen,default LECS address = 39:00:00:00:00:00:00:00:00:00:A3:87:0B:00:00:1D:A3:87:0B:01The LES and BUS have the same ATM address. LES and BUS addresses are constructed from:netprefix + chassis MAC address + ELAN number summed with the numerical value two (2)For examplenetprefix = 39:00:00:00:00:00:00:00:00:00:A3:87:0Bchassis MAC address = 00:00:1D:A3:87:0BELAN number = 3then,default LES and BUS addresses = 39:00:00:00:00:00:00:00:00:00:00:00:1D:A3:87:0B:052.2.2 ELANs Across Multiple SwitchesELANs can exist within a single switch, or they can span multiple switches. When an ELAN spans multiple switches,it’s important that all switches within the group use the same LECS (see note, below). The general rule is: “Within anadministrative domain (a group of switches with related ELANs), there should be one and only one LECS.” For thisreason, never start the LECS on more than one switch within the administrative domain.Note The exception to the statement above is that if LNNI is enabled, multiple,redundant LECS’ and LES/BUS’ can exist within the same administrativedomain. See Section 2.2.7 “Using LNNI.”Note If an uplink, end node, or other ATM switch does not support PNNI, or if itsversion of ILMI is incompatible, it may be necessary to set up a static routebetween the device and the rest of the ELAN. See Chapter 4, "Routing."
