B&B Electronics 516TX-A - Manual - Manual (Page 49)

(Revised 8/4/2009) 49
Ports
By default, the RJ45 ports are auto-sensing for speed, duplexing, and crossover or straight through wiring.
When you select ANY ‘forced’ option, the auto-sensing for that port is disabled for all three parameters and
the ‘remaining’ (unforced) options are set to 100 Mbits, Full Duplex, and straight through cabling. For
example, if you select speed10 for port 2, then port 2 will be: speed10, full duplex, and straight through
wiring. If you need ‘half duplex’ also on port 2, you will have to select it also as auto-sensing will be
disabled for port 2 after you forced speed10. The FX ports are always 100 Mb, and Full Duplex.
Warning:
In a LAN it is best to set ALL devices at autonegotiate, OR to set ALL devices to the
same mode (speed/duplex).
If one end of a link is set to forced speed/duplex, but the other end is not forced, problems can be created.
Why do folks not trust autonegotiation? Many learned (mostly in past or on older equipment) not to trust
autonegotiation. Why? Many implementations were out before the spec was finalized, so did not play well
together. ( We have seen a case where the wiring was cat3 and the devices autonegotiated to 100/full, but the
wiring would not support it.)
On the 500 series, one can autonegotiate, or one can force to any of 4 modes: 100 full, 100 half, 10 full, or
10 half.
If you force one unit into 10/full, and leave another in autonegotiate (the default), the unit in autonegotiation
does not go into 10 full. It goes into 10 half. It gets no autonegotiation response. It easily senses speed
passively, but has no way to sense duplex mode and so uses the "safest" duplex mode - half. Per spec. Thus,
you have one unit at 10 full and the other at 10 half - basically functional but not ideal. The unit at 10 full
transmits without checking for busy and you get more collisions. Also, the 10/full unit does not back off or
retransmit based on the collision domain.
Same happens with one unit forced to 100/full and the other autonegotiating. The autonegotiating unit goes
into 100/half.
Command Description Next prompt:
info Get info on Port Parameters
enabling Enable or disable each port
negotiate Select autonegotiate or not for
each port Enter ports that are to autonegotiate:
speed10 Force 10 Mb speed for each
port Enter forced 10 Mb ports:
speed100 Force 100 Mb speed for each
port Enter forced 100 Mb ports:
half Force half duplex for each
port Enter forced Half Duplex ports:
full Force full duplex for each port Enter forced Full Duplex ports:
crossover Force crossover connection
for each port Enter forced crossover ports:
link10h Advertise 10Mb and half for
each port Enter ports to advertise 10Mb and
half duplex:
filter Configure Collision Filter for
each port First a chance to change the
threshold for collision filter
management, then entry of ports to
be affected.
squelchon
or
squelchoff Squelch more than IEEE
standard (or not) Choice is opposite of current state.