"Joe D." <com> writes:
There's usually a DCE and a DTE. If you have two DCE's, you need a
null modem in the middle to make one end look like a DTE by flipping
transmit and receive, and whatever handshaking lines you are using.
Thus, if you have a computer going to a computer, you'll need a null modem.
>to the Serial A port to ensure that I get POST diags and other boot
>messages at boot time and for maintenance. Does the connection to the
>Serial port A ALWAYS need to be a null-modem connection, or does it
>vary from server to server, and if so, does anyone know a link to a
>quick summary of which Sun servers need what? I've been downloading
>user and field service guides from Sun, but it would be nice to have
>this in a concise tabular format.[/ref]
No, its pretty consistant, you pretty much need a null-modem
everytime. Unless of course, you have a cable already wired as a null-modem.
Some devices (just like in ethernet) try to trick you out by making
themselves look like DTEs instead of DCEs, and then you need a null
modem on the end of your null modem cable if that is what you are using.
FWIW: Sun followed along with the industry to make serial cables on RJ45
constitant to the Cisco standard. One nice feature of the Cisco layout
is that if you roll the cable (ie. pin 1 to 8) and plug it in that
way, you have a null modem. Very convienient.
Sure, what's your budget? Cyclades makes some nice units. You'd
probably be able to find 4-5 without really looking too hard.
Its better to use flat cable instead of twisted pair, but yes, there
are adaptor modules you can buy. Since there aren't many consistant
standards (or, perhaps too many standards that nobody followed one
until recently), they all come unwired, and you are expected to wire
them to whatever standard you want to use.
Or, buy serial cables from your term server vendor at their higher price.
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