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New Member

Serial Interface Reliability

I have a setup of two Cisco 1750 routers connected back to back. Both the routers have WIC-2T serial interface cards.


Both RouterA nd RouterB are connected back to back through Serial Interface0.Encapsulation is HDLC on both sides. Clock Rate is enabled on RouterB(DCE). RouterA Serial Interface IP address is RouterB Serial Interface IP address is "Show INterface Serial 0" command shows that both interfaces are up and protocol is up. But I am not able to ping the S0 interface of both the routers from the respective consoles. In Router A "sh cdp neighbor" command doesn't show any neighbors. In Router B, "sh cdp neigbor" cmd shows the details of Router A. Even if I set the static routing, I am not able to ping. Immediately after booting Router A's serial interface reliability is 250/255 and it gradually decreases to 150/255. Even after clearing the counters, Router A's serial interface shows enormous input errors and no output error.


I connected Router A's serial interface 1 to Router B's serial interface 0., with the above configurations. Absolutely no problem.I am able to ping the serial interfaces of both the routers and the reliability factor of serial interfaces is 255/255.

Can anyone guide me what went wrong in scenario 1?

Thanks and Regards


New Member

Re: Serial Interface Reliability

Could you give the running configurations of both routers




Re: Serial Interface Reliability

revers tha cables and see if the low reliabilty follows the DTE cable or if it stays with router a if it moved then you most likely have a bad cable if it stay I would l look at the WIC . Which interface is showing errors ?

New Member

Re: Serial Interface Reliability

Ensure that there is no mismatch of CDP timers. If in doubt, disable CDP on both routers.


New Member

Re: Serial Interface Reliability

WIC-2T Interface 0 on router A should be the culprit. Can u check with Interface 0 on Router A and Interface 1 with Router B. If still there is reliability issue, definietely its the WIC on interface 0 of router A which is faulty.

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