Serial Back-to-Back Connection

Discussion in 'Cisco' started by Bob Simon, Feb 23, 2009.

  1. Bob Simon

    Bob Simon Guest

    I am putting together a lab with two 2600 routers. I have two serial
    WICs: WIC 1DSU T1 and WIC 2T but I do not have a Smart Serial cable.
    If I buy one, can these two cards be used without an external CSU to
    connect two routers back-to-back?

    Does it matter which side provides clock?

    If I use an RS-232 break out box to verfiy I have the correct leads
    mapped to RJ45 pins, does it mattter whether I get a DCE or DTE Smart
    Serial cable?
     
    Bob Simon, Feb 23, 2009
    #1
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  2. Bob Simon <> writes:
    >I am putting together a lab with two 2600 routers. I have two serial
    >WICs: WIC 1DSU T1 and WIC 2T but I do not have a Smart Serial cable.
    >If I buy one, can these two cards be used without an external CSU to
    >connect two routers back-to-back?


    No, you have one card with a CSU/DSU on it, one card without it. You
    are going to have to match cards or match CSU/DSU's. All this stuff is
    super cheap on eBay though.

    A WIC-1T card is like $9. Another WIC-2T goes for a bit more, but not
    much. A WIC-1DSU-T1 card goes for $25.

    An Adtran TSU CSU/DSU unit is like $15, although I did find one for a penny.

    Cisco 3rd party serial cables are cheap.
    Back to Back smart serial to smart serial are $9. Back to back 60 to 60
    pin are $9. I didn't look hard enough to see if there were any DTE-DCE
    smart serial to 60 pin, but most likely there are.

    The WIC-2T needs smart serial, the WIC-1T is 60-pin.

    So, your choices (in the order I'd do them) are

    Get another WIC-1DSU-T1 and do two WIC-1DSU-T1s back to back.
    You can make your own cross-over T1 cable for this (Wikipedia shows how).

    OR, get another WIC-2T card, and do two serial ports back to back with
    a DTE-DCE smart serial to smart serial cable.

    OR, get an Adtran TSU CSU/DSU, get a smart serial to V.35 cable to
    hook the Adtran up to your WIC-2T, and then run a cross-over T1 cable
    between your WIC-1DSU-T1 and the Adtran CSU/DSU.

    In real life, if you are doing Cisco routers, the odds of you
    installing a new setup with an external CSU/DSU are next to never. The
    odds of you even seeing an external CSU/DSU are probably less than one
    in 10 depending on what areas you are working in. Most likely,
    anything you see will be using the cards with the builtin CSU/DSU's
    like the WIC-1DSU-T1. That is why I suggest using them.

    >Does it matter which side provides clock?


    No, just one side does. Typically the ISP/telco provides the clock,
    but if its private link in a biz setup, then you have to make sure one
    side does.


    >If I use an RS-232 break out box to verfiy I have the correct leads
    >mapped to RJ45 pins, does it mattter whether I get a DCE or DTE Smart
    >Serial cable?


    Eh? I don't think you're going to be able to do that very easily.
    One of the things you will have to test on for CCNA is what a DCE
    is vs. what a DTE is, so you might as well learn up on that now. That
    is (or was at least) a big part to know about.

    While we are dealing with serial ports here, they aren't generally RS-232
    at all, unless you do special conversions over to accomidate that.
    Don't try to think of things in terms of RS-232 at all, you'll just go
    down the wrong path.

    Just buy the correct cabling for what you want to do. Its extremely
    rare for techs to fiddle with breakout boxes for this. With proper
    cables being less than $10, its not worth anybody's time to try to
    hack together something.
     
    Doug McIntyre, Feb 23, 2009
    #2
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  3. Bob Simon

    Bob Simon Guest

    On 23 Feb 2009 15:48:35 GMT, Doug McIntyre <> wrote:

    >Bob Simon <> writes:
    >>I am putting together a lab with two 2600 routers. I have two serial
    >>WICs: WIC 1DSU T1 and WIC 2T but I do not have a Smart Serial cable.
    >>If I buy one, can these two cards be used without an external CSU to
    >>connect two routers back-to-back?

    >
    >No, you have one card with a CSU/DSU on it, one card without it. You
    >are going to have to match cards or match CSU/DSU's. All this stuff is
    >super cheap on eBay though.


    Too bad. I was hoping to connect these two wics for the cost of a
    cable (and that only because I need the specialized connector to plug
    into the WIC).

    I suppose the reason this won't work is because the CSU expects a
    bipolar signal while the WIC-2T is unipolar. Can someone confirm this
    is correct?
     
    Bob Simon, Feb 23, 2009
    #3
  4. Bob Simon <> writes:
    >On 23 Feb 2009 15:48:35 GMT, Doug McIntyre <> wrote:
    >>Bob Simon <> writes:
    >>>I am putting together a lab with two 2600 routers. I have two serial
    >>>WICs: WIC 1DSU T1 and WIC 2T but I do not have a Smart Serial cable.
    >>>If I buy one, can these two cards be used without an external CSU to
    >>>connect two routers back-to-back?

    >>
    >>No, you have one card with a CSU/DSU on it, one card without it. You
    >>are going to have to match cards or match CSU/DSU's. All this stuff is
    >>super cheap on eBay though.


    >Too bad. I was hoping to connect these two wics for the cost of a
    >cable (and that only because I need the specialized connector to plug
    >into the WIC).


    >I suppose the reason this won't work is because the CSU expects a
    >bipolar signal while the WIC-2T is unipolar. Can someone confirm this
    >is correct?



    It won't work because its two totally different protocols and
    signalling between the two ports.

    By default (with no other setup),
    The output of the CSU/DSU card is two pair balanced B8ZS encoding at a
    clock rate of 1.544mbps, framed up in ESF T1 framing.

    The output of the WIC-2T is a synchronous serial bit (which can use
    balanced output or unbalanced) stream with a clock pin, as well as
    extra control pins. (ie. at a minimum its 6 pins, compared to the 4 of a T1).

    How would you account for the seperate clock signals of the serial
    output, let alone the serial bit stream being re-encoded to B8ZS, and
    then framed up in T1 framing to match the CSU/DSU? (other than the
    framer and encoder sections of a CSU/DSU?).

    In PC terms, its like you have an RS-232 port trying to plug into a
    USB jack. You can do it, but you need a chip that talks RS-232 on
    one side, and USB on the other. Its not just a cable.

    The proper stuff to use is *dirt* cheap. The V.35 cables alone used to
    be like $125, let alone those octal-V.35 cables at over $900 a piece.
     
    Doug McIntyre, Feb 23, 2009
    #4
  5. Bob Simon

    Bob Simon Guest

    On 23 Feb 2009 17:24:51 GMT, Doug McIntyre <> wrote:

    >Bob Simon <> writes:
    >>On 23 Feb 2009 15:48:35 GMT, Doug McIntyre <> wrote:
    >>>Bob Simon <> writes:
    >>>>I am putting together a lab with two 2600 routers. I have two serial
    >>>>WICs: WIC 1DSU T1 and WIC 2T but I do not have a Smart Serial cable.
    >>>>If I buy one, can these two cards be used without an external CSU to
    >>>>connect two routers back-to-back?
    >>>
    >>>No, you have one card with a CSU/DSU on it, one card without it. You
    >>>are going to have to match cards or match CSU/DSU's. All this stuff is
    >>>super cheap on eBay though.

    >
    >>Too bad. I was hoping to connect these two wics for the cost of a
    >>cable (and that only because I need the specialized connector to plug
    >>into the WIC).

    >
    >>I suppose the reason this won't work is because the CSU expects a
    >>bipolar signal while the WIC-2T is unipolar. Can someone confirm this
    >>is correct?

    >
    >
    >It won't work because its two totally different protocols and
    >signalling between the two ports.
    >
    >By default (with no other setup),
    >The output of the CSU/DSU card is two pair balanced B8ZS encoding at a
    >clock rate of 1.544mbps, framed up in ESF T1 framing.
    >
    >The output of the WIC-2T is a synchronous serial bit (which can use
    >balanced output or unbalanced) stream with a clock pin, as well as
    >extra control pins. (ie. at a minimum its 6 pins, compared to the 4 of a T1).
    >
    >How would you account for the seperate clock signals of the serial
    >output, let alone the serial bit stream being re-encoded to B8ZS, and
    >then framed up in T1 framing to match the CSU/DSU? (other than the
    >framer and encoder sections of a CSU/DSU?).
    >
    >In PC terms, its like you have an RS-232 port trying to plug into a
    >USB jack. You can do it, but you need a chip that talks RS-232 on
    >one side, and USB on the other. Its not just a cable.
    >
    >The proper stuff to use is *dirt* cheap. The V.35 cables alone used to
    >be like $125, let alone those octal-V.35 cables at over $900 a piece.


    OK, I'm convinced!

    If I purchase another WIC-1DSU-T1 and build a 1,2 - 4,5 crossover
    cable (instead of using another WIC-1T and back-to-back serial
    cables), do I eliminate the clock rate command on one router since the
    internal CSUs provide clocking to both sides?
     
    Bob Simon, Feb 23, 2009
    #5
  6. Bob Simon

    Bob Simon Guest

    On 23 Feb 2009 17:24:51 GMT, Doug McIntyre <> wrote:

    Doug,
    I just searched ebay for WIC-1DSU-T1 and see some cards are listed as
    version 2. Since my card is not labelled Version 2, I presume that
    means I have verison 1. Are there any compatibility issues in
    connecting a WIC-1DSU-T1 V2 directly to a WIC-1DSU-T1 using a
    crossover cable?
    Bob
     
    Bob Simon, Feb 23, 2009
    #6
  7. Bob Simon

    Bob Simon Guest

    On 23 Feb 2009 17:24:51 GMT, Doug McIntyre <> wrote:

    Sorry to split up my questions into separate posts but I I have one
    more:

    The eBay ad for the Cisco WIC-1DSU-T1 V2 DSU/CSU Card says it works
    with the 2600XM. I have one 2611XM and one 2610. Can either version
    of the WIC-1DSU-T1 be used in my 2610?
     
    Bob Simon, Feb 23, 2009
    #7
  8. Bob Simon

    Bob Simon Guest

    On Mon, 23 Feb 2009 12:25:04 -0600, Bob Simon <>
    wrote:

    >On 23 Feb 2009 17:24:51 GMT, Doug McIntyre <> wrote:
    >
    >Sorry to split up my questions into separate posts but I I have one
    >more:
    >
    >The eBay ad for the Cisco WIC-1DSU-T1 V2 DSU/CSU Card says it works
    >with the 2600XM. I have one 2611XM and one 2610. Can either version
    >of the WIC-1DSU-T1 be used in my 2610?


    Please ignore this question. I found the answer here:
    http://www.cisco.com/en/US/products/hw/modules/ps3129/products_tech_note09186a0080093d70.shtml

    WIC-1DSU-T1
    Router families supported
    1600(2) , 1600R(2), 1700(3) , 2600, 2600XM, 3600, and 3700

    WIC-1DSU-T1-V2
    Router families supported
    1700(1) (1720, 1721, 1751, 1760), 2600XMs, 2691, 3631, 3725, 3745, ICS
    7750, 1800 and 2800
     
    Bob Simon, Feb 23, 2009
    #8
  9. Bob Simon <> writes:
    >If I purchase another WIC-1DSU-T1 and build a 1,2 - 4,5 crossover
    >cable (instead of using another WIC-1T and back-to-back serial
    >cables), do I eliminate the clock rate command on one router since the
    >internal CSUs provide clocking to both sides?


    The clock rate command isn't needed, as a T1 has an inherent clock
    rate that it will need to use to match the framing.

    You still will need to generate clock on one side of the link, and
    recover clock on the other side.

    (ie.
    int ser 0/0
    service-module t1 clock source internal

    to generate the clock for this side with a WIC-1DSU-T1 card).

    The last arg opposite is 'line' to recover the clock from the line,
    and is the default so you don't see it.
     
    Doug McIntyre, Feb 23, 2009
    #9
  10. Bob Simon <> writes:
    >On 23 Feb 2009 17:24:51 GMT, Doug McIntyre <> wrote:
    >I just searched ebay for WIC-1DSU-T1 and see some cards are listed as
    >version 2. Since my card is not labelled Version 2, I presume that
    >means I have verison 1. Are there any compatibility issues in
    >connecting a WIC-1DSU-T1 V2 directly to a WIC-1DSU-T1 using a
    >crossover cable?


    Yes, a T1 is a T1, as long as you match the framing and encoding, you
    should be able to talk to anything that talks T1.

    As you later saw, the version 2 hardware works only in newer hardware
    (I seem to remember having a huge problem finding an IOS image for the XM
    chassis that could support it, even though it is listed).
     
    Doug McIntyre, Feb 23, 2009
    #10
  11. Bob Simon

    Bob Simon Guest

    On 23 Feb 2009 20:31:48 GMT, Doug McIntyre <> wrote:

    >Bob Simon <> writes:
    >>On 23 Feb 2009 17:24:51 GMT, Doug McIntyre <> wrote:
    >>I just searched ebay for WIC-1DSU-T1 and see some cards are listed as
    >>version 2. Since my card is not labelled Version 2, I presume that
    >>means I have verison 1. Are there any compatibility issues in
    >>connecting a WIC-1DSU-T1 V2 directly to a WIC-1DSU-T1 using a
    >>crossover cable?

    >
    >Yes, a T1 is a T1, as long as you match the framing and encoding, you
    >should be able to talk to anything that talks T1.
    >
    >As you later saw, the version 2 hardware works only in newer hardware
    >(I seem to remember having a huge problem finding an IOS image for the XM
    >chassis that could support it, even though it is listed).


    Doug,
    Thanks very much for all your help. You've save me a lot of time and
    probably some money by steering me away from buying a specialized
    cable that wouldn't do me any good. I especially appreciate the
    config help with "service-module t1 clock source internal" because I
    had no idea that command was needed (or even existed).

    Finally, based on your comment about limited IOS support for
    WIC-1DSU-T1 V2 , I'm going to buy the original one.
    Bob
     
    Bob Simon, Feb 23, 2009
    #11
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