IBM SC30-3681-08 manual Esi, ATM Addresses of LAN Emulation Components

Overview of LAN Emulation

End stations obtain their Network Pre®x from the switch and form their own addresses by appending an ESI and selector. These addresses must then be registered with the switch, which rejects the registration if the ATM address is not unique.

ESI

Each ATM interface on the router has a universally administered, or burned-in, MAC address. You can use the MAC address as an ESI for some or all of the router's ATM addresses. Alternatively, you can de®ne up to 64 locally administered ESIs on each interface. If every end system uses its universally administered MAC address as its ESI, then ATM addresses are guaranteed to be unique. This eases the con®guration burden. However, using locally administered ESIs can ease problem determination. You can use any combination of universal or locally administered ESIs.

One way to obtain a unique ATM address is to use a burned-in IEEE MAC address as the ESI and to locally choose a unique selector. By default, the router uses the MAC address of the ATM interface as the ESI in its ATM addresses. Additional ESIs can be con®gured on each ATM interface.

Each ESI can have up to 255 associated selectors (0x00 through 0xff). The range of selectors is partitioned into two subranges, a con®gured selector range and an automatically assigned selector range. The ATM interface parameter max-con®gured-selector gives the upper bound on the con®gured selector range.

The ATM components on the router have various ways of choosing a selector.

Some components require you to explicitly con®gure a selector from the con®gured selector range. LES/BUSs are an example of such a component. Other components, such as Classical IP clients, allow the selector to be automatically assigned at run-time. You do not have to choose the selector because the router does this when it activates. This selector is not guaranteed to be consistent across router restarts. Automatic selector assignment is useful only for those ATM components whose ATM address does not have to be already known by other network devices.

You must con®gure ATM before you con®gure emulated LANs, bridging or routing.

ATM Addresses of LAN Emulation Components

In general, ATM addresses must be unique among LAN emulation components. The only exception is that a LES and BUS serving the same ELAN can share an ATM address, as is the case on the router.

LAN emulation components are con®gured for a particular ATM interface. You can decide to use the burned-in MAC address as the ESI portion of the ATM address of the component or you can select one of the locally-administered ESIs that have been de®ned for the ATM interface. Multiple LE components can share the same ESI if they have unique selectors. By default, the con®guration interface assigns each LE component a unique selector value for the con®gured ESI; however, you can override this assignment and explicitly con®gure a particular selector value.

An ATM interface parameter determines the number of selectors per ESI reserved for explicit assignment. The remainder are available for dynamic assignment by the ATM interface at run-time. LE components use only the selectors reserved for

258MRS V3.2 Software User's Guide