Cabletron Systems 9A100 manual ATM Addressing for LAN Emulation, ELANs Across Multiple Switches

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3.2.1ATM Addressing for LAN Emulation

The SmartSwitch 9A100 provides a default format for ATM addresses used by LAN emulation. The default format is constructed as follows:

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 20-byte ATM address of the LECS is:

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.

Note 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.”

3-6 SmartSwitch 9A100 User Guide