LANE Components
To accept how LANE works aural a beyond switched network, you should aboriginal understand
how emulated LANs (ELANs) alter from basal LANs (VLANs). Recall that basal LANs
are acclimated on Catalyst switches as a agency to articulation cartage into analytic networks. VLANs can
also be trunked amid switches. Similarly, ELANs are acclimated by ATM accessories to segment
traffic into analytic networks. However, ELANs abide alone aural the ATM domain. ELANs and
VLANs abide abstracted except area they are physically bridged in Catalyst switches that
support both.
This aberration is illustrated in Figure 6-3 as a arrangement consisting of two Catalyst switches
connected by two ATM switches. Anniversary Catalyst about-face has ports assigned to VLAN 1. Note that
each VLAN 1 is cogent alone to the bounded switch, and that some added agency charge be acclimated to
214 Chapter 6: Trunking with ATM LANE
logically affix the two VLANs. An ELAN exists on anniversary Catalyst about-face as ELAN 1. LANE
makes logically abutting the ELAN amid switches beyond an ATM arrangement possible.
Figure 6-3 An Archetype of VLAN and ELAN Functionality
Because LANE charge challenge the functions of a LAN, accede the afterward characteristics of
a LAN:
• Layer 2 MAC addresses—All stations on a LAN use different 6-byte MAC addresses.
• Concrete or analytic connectivity—All stations on a LAN are physically connected
through hubs or switches, and logically affiliated through VLANs and trunking on
switches.
• Broadcasts and multicasts—LANs acquiesce one-to-many manual of frames in the
form of broadcasts and multicasts.
LANE has been advised with detached apparatus to abode these and added LAN
requirements. For anniversary ELAN that exists in a network, the afterward LANE apparatus are
used:
• LAN Emulation Client (LEC)—The LEC provides the basal ELAN action on each
ATM accessory area an ELAN affiliation is needed. The LEC emulates an interface to a
traditional LAN and provides abstracts forwarding, abode resolution, and MAC address
registration with added LANE components. Anniversary LEC can acquaint with added LECs
in the arrangement over ATM basal approach access (VCCs) battling concrete or
logical LAN connectivity.
ATM
switches
Catalyst A Catalyst B
VLAN 1
ELAN 1
VLAN 1
LAN Emulation (LANE) 215
• LAN Emulation Server (LES)—The LES (one per ELAN) acts as a axial ascendancy point
for all LECs in an ELAN. Anniversary LEC charge annals its MAC addresses with the LES so that
the LES can accommodate MAC abode to NSAP abode translation. The LES additionally maintains
connections to anniversary LEC to accommodate ascendancy advice to all ELAN members.
• Advertisement and Unknown Server (BUS)—Because ATM does not abutment broadcast
functions, the BUS is acclimated to challenge LAN broadcasts. Any LEC that needs to accelerate a
broadcast sends it anon to the BUS. The BUS is again able to advanced the advertisement to
all added LECs (and all stations in anniversary LEC) through a point-to-multipoint VCC. The
BUS takes affliction of queuing and sequencing advertisement and multicast frames over the pointto-
multipoint VCC so that the frames access in the actual adjustment at the LECs.
• LAN Emulation Configuration Server (LECS)—The LECS (only one per
administrative domain) acts as the axial authoritative ascendancy point for all ELANs in a
domain. The LECS maintains a database of ELANs and the ATM addresses of the LESs
that ascendancy anniversary ELAN. Anniversary LEC charge concern the LECS to ask for associates in an
ELAN and to appeal the NSAP abode of the corresponding LES.
Figure 6-4 shows a archetypal LANE network. Three Catalyst switches are ATM bend devices;
each is affiliated to the ATM network. LANE is configured to abutment two ELANs associated
with two VLANs present on anniversary switch. Therefore, anniversary Catalyst is configured with two LEC
components—one for anniversary ELAN/VLAN. The actual LANE apparatus can be
configured arbitrarily. In this example, the LECS is configured on Catalyst B. For ELAN1, a
LES/BUS brace is configured on Catalyst A, and a LES/BUS brace for ELAN2 is configured on
Catalyst C. Notice that both LES/BUS pairs could accept been configured on a distinct Catalyst
along with the LECS.
Figure 6-4 An Archetype LANE Arrangement with Component Placement
Catalyst A Catalyst C
ELAN 1: LEC 1
ELAN 2: LEC 2
Catalyst B
ELAN 1: LEC 1
ELAN 2: LEC 2
LECS
ELAN 1: LEC 1
ELAN 2: LEC 2
LES/BUS1 LECS/BUS