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45984 Views 18 Replies Latest reply: Sep 15, 2013 10:17 PM by Uma Shankar V. RSS 1 2 Previous Next

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DTE and DCE connector?

Mar 21, 2013 4:23 PM

Mustafiz 49 posts since
Sep 4, 2012

Heyy when you try connecting two routers in a WAN,i read it happens this way..R1 connects to CSU/DSU via a short cable at one end..then to CO via telco wires..and this repeats at the other end.

 

just telme if router is the DTE end and CSU/DSU is the DCE end what connector is used to connect them both? i.e how are the DCE and DTE connected to each other?

 

Thanks

  • Adrian Kells 156 posts since
    Jul 5, 2012
    Currently Being Moderated
    1. Sep 7, 2012 8:41 PM (in response to Mustafiz)
    Re: DTE and DCE connector?

    The ISP determines what your clock speed and duplex and that sort of thing is for your serial wan link. That then makes them the DCE end.

    http://www.dantrak.at/static/upload/images//5/4/PrWqwh6r4G_mcFYrGXeB6_SSDB60_big_big.jpg

     

    The link above is an example of a DTE,DCE cable

     

    https://learningnetwork.cisco.com/message/230827#230827

     

    The above thread also goes into good detail that might help clear it up for you.

     

    Also different routers can have 2 kinds of serial interfaces (as far as I know from my studies) theres a a T1 WIC which is the older bigger style with alot of pins, the WIC 2T I believe is the thinner one that sort of looks like a type of SCSI connection.

     

    This link below will explain a WIC 2T interface card.

     

    http://www.cisco.com/en/US/products/hw/routers/ps274/products_tech_note09186a00800b0858.shtml

     

    This one then explains the WIC 1T

     

    http://www.cisco.com/en/US/products/hw/modules/ps3129/products_tech_note09186a00800b0859.shtml

     

    As you can see, very different connections, but both are serial WAN interfaces. Its important to know the difference.

     

    Another thread that might help with the CSU DSU Explaination -

     

    https://learningnetwork.cisco.com/thread/28073

     

    Sorry about all the information - Hope it helps (please correct if I explain something wrong or overly complicated anything).

     

    Regards,

     

    Adrian

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  • Muhammad Arshad 36 posts since
    Jun 9, 2009
    Currently Being Moderated
    2. Sep 7, 2012 8:46 PM (in response to Mustafiz)
    Re: DTE and DCE connector?

    Dear Mustafiz,

     

    You need a sereil cable V.35.

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  • Currently Being Moderated
    3. Sep 7, 2012 11:28 PM (in response to Mustafiz)
    Re: DTE and DCE connector?

    Mustafiz, whether using PT or real routers, when we connect routers like this, its called a serial back to back connection.  Its only done in labs to simulate a WAN (its actually a kind of crossover cable). In the real world there would be some kind of intervening device, such as a CSU/DSU.

     

    Its the CABLE itself that determines which end of the link is DCE or DTE.

     

    So, in packet tracer do this: connect two routers using the serial cable that has the little clock icon on it.  You don't need to add IP addresses, just issue the no shutdown command on each serial interface.

     

    Now, on the side that has the little clock icon, run the show controllers command, like this:

     

    Router#show controllers s0/0/0 (or whatever serial you have)

    Interface Serial0/0/0

    Hardware is PowerQUICC MPC860

    DCE V.35, clock rate 2000000

     

    Then run the same command on the other end of the link...what do you see?

     

    Last, flip the cable and run the commands again.

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  • Adrian Kells 156 posts since
    Jul 5, 2012
    Currently Being Moderated
    5. Sep 8, 2012 6:40 PM (in response to Mustafiz)
    Re: DTE and DCE connector?

    Mustafiz,

     

    https://learningnetwork.cisco.com/thread/28073

    The above link gives a really good amount of images that really explain a wan set up.

     

    In short with that whole thread, you have a router(DTE) which connects to a CSU/DSU(DCE) via a v.35 synchronous serial cable. The router(DTE) takes the smaller male connector and the CSU/DSU(DCE) takes the bigger female connector, this connects the two together and the clock rate and other details are provided to the router(DTE) via the CSU/DSU(DCE). In the particular thread above, the CSU/DSU is then connected via a T1 service to an ISP, using an apparent RJ-48 connector which is a little different to an RJ-45.

     

    Here is the image of it all together:

     

    https://learningnetwork.cisco.com/servlet/JiveServlet/showImage/2-136969-36023/dsu-router-connection.jpg

     

    Hopefully this will shed some light!

     

    Also: Thank you Keith Barker for this picture and his explination that I was able to refer to.

     

    Regards,

     

    Adrian

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  • Adrian Kells 156 posts since
    Jul 5, 2012
    Currently Being Moderated
    6. Sep 8, 2012 7:01 PM (in response to Mustafiz)
    Re: DTE and DCE connector?

    This is a back to back WAN connection using 2 routers on Packet Tracer as an example also. Kev is deffinitly right when using the cable can also determine who is DCE and who is DTE in a WAN link when its set up this way, I just chose R1 as mine, when making this sort of connection, you chose DCE Serial as the cable and click which router you want as the DCE and then connect to the other device as the DTE.

    DCE to DTE B2B.jpg

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  • Mohamed Sobair 344 posts since
    Oct 21, 2008
    Currently Being Moderated
    9. Sep 9, 2012 9:20 AM (in response to Mustafiz)
    Re: DTE and DCE connector?

    In a Back to Back Serial Connection, the Clock must be set at the DCE side, a source of clocking is always needed in Asynchronous Serial Link, because the routers are connected directly, its configured at the DCE side.

     

    If the routers are not directly connected, ie: the Router is connected to the Telco CSU/DSU, no need for the Clock rate to be configured at the serial interface, as the Source of Clocking is provided by the CSU/DSU.

     

    HTH

    Mohamed

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  • Currently Being Moderated
    10. Sep 9, 2012 12:04 PM (in response to Mohamed Sobair)
    Re: DTE and DCE connector?

    exactly

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  • Adrian Kells 156 posts since
    Jul 5, 2012
    Currently Being Moderated
    12. Sep 10, 2012 6:25 PM (in response to Mustafiz)
    Re: DTE and DCE connector?

    Did you mean, why do we need to use IP addresses on the WAN link?

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  • Adrian Kells 156 posts since
    Jul 5, 2012
    Currently Being Moderated
    14. Sep 11, 2012 6:28 PM (in response to Mustafiz)
    Re: DTE and DCE connector?

    Mustafiz,

     

    Im sure theres more to the reasoning behind it that I know of, but my understanding is that if you dont have IP addressing over WAN, then the routing won't work between devices. You wont have a next hop IP when example RIPv2 attempts to find the best route between hosts. You can configure static routes without using a next hope by specifiying it to go out a specific interface, but I still believe it needs IP addressing to correctly work still. NAT wouldnt work either if you didnt have an IP address, example: if your network had a WAN Link directly to the ISP just for internet, if that WAN Didnt have an IP address you wouldnt be able to use NAT/PAT to access the internet from private IP addresses.

     

    Again I'm sure theres a better reason than that but thats what comes to mind as what would happen if you didnt. A layer 3 device handles and requires layer 3 addressing.

     

    Hope this helps,

     

    Adrian

     

    [Please add to this if I've missed something or didnt explain it properly, as it would benefit me also]

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