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New Member

Checking router serial ports

Hi all,

To confirm the serial ports of two routers are working, I am connecting them back to back by two V35 cables(V35 male & V35 female), and I know one router should be DCE and whilst the other should be DTE. Here are my questions are:

1) How can I make this test work? I've heard there are DTE & DCE cables, then how can I identify a DTE or DCE cable? By the female or male connector on the cable itself or some other methods?

2) Where should I enable clocking? On the DCE side or DTE side?

I've tried different combinations of above two but with no luck, can u guys shed me some light on this?




Re: Checking router serial ports

Here are some answers:

1) Yes, physically by the male and female connector.

Also, you can identify a DTE or DCE cable through

a label on the cable itself (if they have).

I think its like a white sticker with a "DTE" or "DCE" label.

From your router, you can also use

"show controllers serial" to determine if the cable

connected to the serial port is a DTE or DCE.

2) Clocking is on the DCE side.

Assuming that Router1 uses the DTE cable:


interface serial 0

ip address ***** *****

no shutdown


interface serial 0

ip address ***** *****

clock rate

no shutdown

Hope this helps.

New Member

Re: Checking router serial ports

Thanks for your reply a.manosca .

I think my current male & female cables are both DTE type as the outputs of "show controller serial 0" are:

" DTE V.35 clocks stopped"

Therefore does that mean both male or female V35 cables can be DCE and cables are only identifed by plugging to a router serial port if there is no sign of DTE or DCE marked on the cables..

Thks again,



Re: Checking router serial ports

You mentioned this on your first post:

"By the female or male connector on the cable itself or some other methods?"

So I assumed you have identified the male (with "exposed" pins) as the DTE

and a female (with "holes") as the DCE.

If you typed the "show controller serial 0" on the TWO routers,

you should look for an output something like:

Router# show controllers serial

MK5 unit 0, NIM slot 1, NIM type code 7, NIM version 1

idb = 0x6150, driver structure at 0x34A878, regaddr = 0x8100300

IB at 0x6045500: mode=0x0108, local_addr=0, remote_addr=0

N1=1524, N2=1, scaler=100, T1=1000, T3=2000, TP=1

buffer size 1524

DTE V.35 serial cable attached

Based on experience, I haven't seen a MALE V.35 cable used as a DCE.

Why? Because the V.35 DTE cable is used to connect to a DCE device,

typically a Modem. I don't know how this sounds but you can say:

"Male (DTE) cables have sticks and female (DCE) cables have holes".

These links should help:

I hope I made it quite clear.


New Member

Re: Checking router serial ports

Thanks for your information clearing up the cable conventions, from my observations i guess there may be an issue with the DCE(male) cable as it never shows any sign of DCE when attached to the two routers, therefore I will get another DCE cable to verify.

WIth thanks & regards,


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