E3Switch DS3 Operating information manual - page 13
Chapter 5: Operating Modes and Configuration
Packet Flow
Port to Port Packet Flow
LAN-to-LAN
Certain firmware versions allow LAN-to-LAN packet flow to 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
Once a PPPoE session is established, all PPPoE packets are passed from LAN to WAN unfiltered and
unmodified. All PPP packets from the WAN are passed to the LAN likewise.
Loopback
Certain firmware versions allow packet flow from DS3 ports to LAN to be configured to automatically halt
in certain situations in which the converter is receiving loopback data. 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 following hardware for the two LAN ports exist on all converters shipped:
●
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.
●
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.
LAN Port Speed
Typically, set the PPPoE LAN port speed to GigE 1000Mbit/s to allow packet-lengths greater than 1500-
bytes and up to 9600 bytes. Set the management LAN port speed to 100BASE-TX to avoid DMA
underflow/overflow errors of the converter.
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