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New Member

Serial int down when connecting to Alcatel 3612 Mux.


I have this Cisco 2621XM router serial interface connecting to a data port of the Alcatel mux using a v.35 dte cable. Configure as normal lease line connection in the router. Performing a back to back testing is fine. But, when it's connected to the mux, the serial interface is down. What would be the problem? Is it the router side or multiplexor side?

Appreciate your comments...

Thanks alot,

Moh Fun.

  • Other Network Infrastructure Subjects

Re: Serial int down when connecting to Alcatel 3612 Mux.

Appearently, the problem is not in the router as the back-to-back situation works. How did you do that with cabling? You cannot directly connect two routers with each a V35 DTE cable. Therefore I suppose that you used a V35 Female on one side. You would also need to set a clockrate on this (DCE-)side. Did you remove this setting?

For further troubleshooting, it is important to know wheter you are having an interface that is down or just the line protocol.



New Member

Re: Serial int down when connecting to Alcatel 3612 Mux.

Hi Leo,

First of all, thanks alot. For the back-to-back testng, yes, a DCE cable with clocking configuration is done on one of the router. After the testing, the clockrate config is removed. Currently, the 2 routers that are connecting to the mux respectively at 2 different site is using a v.35 dte cable thru the serial int.

From the output of sh ip int brie, it is noticed that both interface & line protocol is down. Is there anything that can be done on router side to identify where's the root of the problem?

Warm regards,

Moh Fun.

Re: Serial int down when connecting to Alcatel 3612 Mux.

The fact that your interface is down inadvertedly points to the MUX. On a valid port you should have DSR, CTS, and DCD in an active state. If this is not the case, please check the interface configuration of the MUX.

In most cases, the DCE will also generate the clock signal for the link.

Check wheter there is a valid channel configured between the two Cisco's and that your MUX is generating the clock signal.




Re: Serial int down when connecting to Alcatel 3612 Mux.

Who is going to be supplying the clock in this situation ? The router or the Mux ?

If it is the mux make sure you are using a DTE cable on your serial interface , A DCE cable will not work , also make sure that you have a valid clock source .