Operations Manual
53
Background
The LECS maintains configuration parameters and a membership table of
LECs for all ELANs in your ATM network. This membership table contains a
list of ELAN members as well as their associated MAC to ATM addresses.
The LECS also provides these addresses to requesting clients (LECs).
ATI’s ATM software implements ATM Forum’s LEC. LEC implementation,
in turn, conforms to the LAN Emulation Specification 1.0. That is, your
switch implements LEC functionality between a legacy Ethernet device and
an ATM network. This is important since connection to the LAN Emulation
Service (LES) is through LECs.
In short, with v.2.4, all LECs (switches) — as well as all devices
(workstations, PCs, printers, scanners) attached to those LECs — can be
automatically configured from the LECS (for Ethernet connectivity only) or
manually through the
Port to ELAN configuration
screen (from the
LAN emulation
submenu). When the LES or LECS is not available, you
can still assign membership to your user-defined ELAN by using the
“FIXED ELAN” assignment in the
Port to ELAN configuration
screen.
Four
Configurations
Local Ethernet forwarding can be defined within four environments:
1.
There is no ATM Physical Media Module installed in the switch. Without
an ATM Physical Media Module installed the device operates as a
standalone Ethernet switch. In order for the device to switch packets
locally all ports must be configured to “Fixed ELAN: all devices on this
port forced to port’s ELAN” located on the
Port to ELAN
configuration
screen “Port to ELAN Configuration Submenu — AT-
S13” on page 63 or “Port to ELAN Configuration Submenu — AT-S16” on
page 65 both of which are derived from the “LAN Emulation Menu” on
page 60).
NOTE
Please note that the Port to ELAN Configuration Submenu default address is
MAC, not FIXED. This means that, if the LECS becomes inoperative for any
reason, the default is lost as well and ports must be reassigned to FIXED to
be operative.
2.
An ATM Physical Media Module is installed in the switch. Therefore a
configuration request will be sent to the LECS as each new device is
attached. A device that receives a positive response from the LECS will
join an ELAN. A device that receives a negative response will join the
“default” ELAN (if it has been configured).
If, however, the switch cannot make a connection to the LECS all ports
that have been previously configured with a “Fixed ELAN” assignment
can still forward data locally.
3.
All ELANs are configured and operational when, suddenly, the LECS
connection is terminated.
All devices currently registered in the Forwarding Table are unaffected.
They will continue to forward packets on the ELANs that they have
previously joined locally.
