Chapter 5: Operating Modes and Configuration
Packets arriving at one telecom port will not be passed out the other, so it is not possible to use one dual-
channel converter in a 3-unit topology at the junction of a Y or V; use two converters at such a junction
with a LAN switch or router to properly control traffic flow to the branches of such a topology.
LAN-to-LAN
LAN-to-LAN packet flow can be enabled, if desired, in units where the second SFP/LAN port has been
enabled/purchased. LAN-to-LAN unidirectional flow for monitoring may also be configured if desired.
LAN-to-LAN flow can result in dropped packets if the destination LAN port bandwidth setting is too low.
An example would be 2x 44Mbit/s traffic from a dual-DS3 and > 12Mbit/s traffic from the other LAN port
exceeding 100Mbit/s of a 100Base-TX LAN port which was receiving both DS3 and LAN-to-LAN traffic.
The unit will attempt to preserve incoming DS3/E3 packets while dropping LAN-to-LAN packets in such
an instance.
LAN-to-LAN should be used cautiously in combination with management or data-only LAN port settings.
The blocking of a subset of traffic can result in network and spanning tree topologies which can be
inappropriate or difficult to diagnose.
Forwarding
Certain packets are not forwarded. Management unicast packets destined for the local unit are not
forwarded. Dual-LAN units can be configured for management-only LAN ports which will drop incoming
unicast packets not destined for an E3Switch MAC address. Spanning-tree packets are passed transparently
between LAN and DS3/E3 ports, but not necessarily between LAN and LAN ports.
Loopback
Packet flow from DS3 ports to LAN can be configured to automatically halt in certain situations in which
the converter is receiving loopback data. This prevents attached LAN equipment from becoming confused
or disabling ports when it receives packets containing a source-MAC-addresses identical to its own, unique
source address. For firmware shipping since August 5
th
, 2009, any DS3/E3 loopback can be detected.
For
firmware prior to August 5
th
, 2009, the automatic loopback traffic disable will only occur if the local
converter has requested the remote to loopback. This occurs when an SNMP request sets the local
converter dsx3SendCode variable to dsx3SendLineCode, which requests the remote converter to loopback
DS3 data received. DS3 loopback initiated by the carrier or any source other than described above cannot
be recognized as loopback data and the setting described will be irrelevant.
LAN Port Settings
The hardware for two LAN ports exist on all converters shipped; however, entry-level models ship with
only the RJ-45 100Base-TX mode enabled. See upgrades section of this manual to enable these additional
features if required:.
●
GbE, GigE 1000Base-T for the RJ-45 LAN port2.
●
Jumbo frames (9600 bytes).
●
SFP LAN Port 1 which can accept optical or copper (100/1000) SFP transceivers.
●
If SFP port has been enabled, either LAN port can be configured as a dedicated out-of-band
management port if desired.
See the “Interoperability” section of this manual for information on packet lengths and detailed port
connection/autonegotiation discussion.
The autonegotiation mode of the converter must match the autonegotiation mode of attached LAN
equipment.
If autonegotiation is enabled on the converter it must be enabled on the attached equipment. If
disabled on the converter, it must be disabled on the attached equipment. This requirement is necessary to
fulfill 802.3 standards which mandate a fallback to half-duplex operation if an autonegotiation mismatch
exists. The converters require full duplex to operate.
14
