When to use a null model cable or adapter? - SUN

This is a discussion on When to use a null model cable or adapter? - SUN ; Hi all; I am managing an environment with numerous Sun servers, from old Ultra-XX to V120 and V210 blades, to 280R, 420R, and V880's. Very few of them have consoles attached. I would like to set up a terminal server ...

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Thread: When to use a null model cable or adapter?

  1. When to use a null model cable or adapter?

    Hi all; I am managing an environment with numerous Sun servers, from
    old Ultra-XX to V120 and V210 blades, to 280R, 420R, and V880's. Very
    few of them have consoles attached. I would like to set up a terminal
    server environment to enable console connectivity to them for local and
    remote access to console. I am looking for some advice on the 'basics'
    I will need; particularly with regard to 'null modem' cabling.

    >From my reading thus far, I understand that I will want to connect up

    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.

    Also, can anyone recommend any particular manufacturer of terminal
    servers or switches, or whatever that would meet my needs? I'm looking
    for capacity of 20 - 25 servers, with the ability for local access
    (terminal in the actual computer room) and remote access to the switch,
    where I could then select whichever server's port I needed. Are there
    adapters available that turn a regular ether cable into a null modem
    cable (say, a two piece connector set; one in Serial A, the other on
    the Terminal serverport , and they're wired such that all you need do
    is connect them with an ether?).

    Any pointers, past experiences, tips and gotchas gratefully appreciated
    and acknowledged.

    Joe


  2. Re: When to use a null model cable or adapter?

    "Joe D." writes:
    >I will need; particularly with regard to 'null modem' cabling.


    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.

    >>From my reading thus far, I understand that I will want to connect up

    >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.


    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.

    >Also, can anyone recommend any particular manufacturer of terminal
    >servers or switches, or whatever that would meet my needs? I'm looking
    >for capacity of 20 - 25 servers, with the ability for local access
    >(terminal in the actual computer room) and remote access to the switch,
    >where I could then select whichever server's port I needed.


    Sure, what's your budget? Cyclades makes some nice units. You'd
    probably be able to find 4-5 without really looking too hard.

    > Are there adapters available that turn a regular ether cable into a
    >null modem cable (say, a two piece connector set; one in Serial A,
    >the other on the Terminal serverport , and they're wired such that
    >all you need do is connect them with an ether?).


    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.

    The canonical page to refer to is at..

    http://www.sunhelp.org/unix-serial-port-resources/

  3. Re: When to use a null model cable or adapter?

    In comp.unix.solaris Joe D. wrote:

    > From my reading thus far, I understand that I will want to connect up
    > 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.


    A "straight-through" cable is useful when going from a modem to a
    terminal. They're designed for this. However, when going from a
    terminal to a terminal, you can't. They both talk on the same pins, so
    the cable has to swap them. This is the basic bit of the null-modem.

    You need it any time you're attaching two terminal-like (DTE) ports
    together. All Sun boxes and PCs will have DTE serial ports.

    http://www.sunhelp.org/unix-serial-p...erial-pinouts/

    Dedicated terminal server hardware may be wired any way they like.
    You'd need to refer to their documentation for what is right to do.

    --
    Darren Dunham ddunham@taos.com
    Senior Technical Consultant TAOS http://www.taos.com/
    Got some Dr Pepper? San Francisco, CA bay area
    < This line left intentionally blank to confuse you. >

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