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

End stations obtain their Network Preﬁx 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 ATMaddress is not

unique.

ESI

Each ATMinterface on the router has a universally administered, or burned-in, MAC

address. Youcan use the MAC address as an ESI for some or all of the router’s

ATM addresses.Alternatively, you can deﬁne up to 64 locally administered ESIs on

each interface. If every end system uses its universally administered MAC address

as its ESI, then ATMaddresses are guaranteed to be unique. This eases the

conﬁguration burden. However, using locally administered ESIs can ease problem

determination. Youcan use any combination of universal or locally administered

ESIs.

One way to obtain a unique ATMaddress 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 ATMinterface as the ESI in its ATM addresses. Additional ESIs

can be conﬁgured on each ATMinterface.

Each ESI can have up to 255 associated selectors (0x00 through 0xff). The range

of selectors is partitioned into two subranges, a conﬁgured selector range and an

automatically assigned selector range. The ATMinterface parameter

max-conﬁgured-selector gives the upper bound on the conﬁgured selector range.

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

Some components require you to explicitly conﬁgure a selector from the conﬁgured

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. Youdo 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 thoseATM

components whose ATMaddress does not have to be already known by other

network devices.

Youmust conﬁgure ATM before you conﬁgure emulated LANs, bridging or routing.

ATM Addresses of LAN Emulation Components

In general, ATMaddresses 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 conﬁgured for a particular ATMinterface. You can

decide to use the burned-in MAC address as the ESI portion of the ATMaddress of

the component or you can select one of the locally-administered ESIs that have

been deﬁned for the ATMinterface. Multiple LE components can share the same

ESI if they have unique selectors. By default, the conﬁguration interface assigns

each LE component a unique selector value for the conﬁgured ESI; however, you

can override this assignment and explicitly conﬁgure a particular selector value.

An ATMinterface 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

Overview of LAN Emulation

258 MRS V3.2 Software User’s Guide