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serial & line protocol is down

recently i have installed cisco 2800 series router with E1 controler contected to my ISP after configuring controller as well as NAT it was working fine now suddenly i am geting Serial 0/2/0:0 down as well as line protocol down . when i give loop to my ISP router he get serial & protocol up but when they give loop to our router we still get interface down . is this media issue or some thing with router controller any help ?


Re: serial & line protocol is down


Could you please post a sh controller and a sh interface ?



Cisco Employee

Re: serial & line protocol is down

I think the problem lies local in your site. Let me know hows the conetcivity to the serial port. I believe that you are using some CSU/DSU which is connected to ISP's MDF and then from IDF its going directly to ISP's network.

From where did you give the loop towards the ISP, from your router, from your CSU/DSU towards ISP or from MDF to the ISP.

Try the following:

1. Give loop from your CSU/DSU towards the local router interface.

2. If you get the loop then, Give the loop from your MDF towards router.

3. If you get the loop then ask ISP to give loop towards your router and check the status.

If you dont get link in any of the step above then try torubleshooting the local connectivity or media issues.

HTH,Please rate if it does.

-amit singh

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