Creating an Emulated LAN | IP Over ATM and LANE |
3.2.1ATM Addressing for LAN Emulation
The SmartCell
netprefix + the MAC address of the device + a Selector Byte
Where the netprefix is constructed from
39 + nine zero bytes + the last three bytes of the switch’s MAC address
The Selector Byte specifies to whom the ATM address belongs.
00 = LEC
01 = LECS
02 = LES or BUS
For instance, if the switch’s MAC address is 00:20:D4:14:41:80, then the
39:00:00:00:00:00:00:00:00:00:14:41:80:00:20:D4:14:41:80:01
Where
39:00:00:00:00:00:00:00:00:00:14:41:80 = netprefix 00:20:D4:14:41:80 = the switch’s MAC address
01 = the Selector Byte indicating that this is the LECS
Additionally, within both the LES and BUS addresses, the byte that corresponds to the last byte of the MAC address is summed with the ELAN number. For example, the ATM address of the LESs on ELAN000, ELAN001, and ELAN010 are
LES for ELAN000 = 39:00:00:00:00:00:00:00:00:00:14:41:80:00:20:D4:14:41:80:02
LES for ELAN001 = 39:00:00:00:00:00:00:00:00:00:14:41:80:00:20:D4:14:41:81:02
LES for ELAN010 = 39:00:00:00:00:00:00:00:00:00:14:41:80:00:20:D4:14:41:8A:02
3.2.2ELANs Across Multiple Switches
ELANs 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. The general rule is: “Within an administrative domain (a group of switches with related ELANs), there should be one and only one LECS.” For this reason, never start the LECS on more than one switch within the administrative domain.
2p›F If an uplink or end node does not support PNNI, or if its version of ILMI is incompatible, it may be necessary to set up a static route between the device and the rest of the ELAN. See Section 4.2, “ATM Routing.”
