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New Member

Error message: Line protocol is down.

Hi. I'm new to the networking industry and I'm implementing a frame relay test environment with 3 Cisco routers. The first router is being configured as a FR switch, which is connected to the main backbone. The other 2 routers are then connected to the first router. Everything seems to have been configured and connected correctly, but all the routers are giving me this error "Serial( X ) is up, line protocol is down." I can't seem to figure out what the problem is. I would appreciate any input, suggestions, help.


New Member

Re: Error message: Line protocol is down.

Did you set lmi type?

New Member

Re: Error message: Line protocol is down.

This indicates that the router considers the serial interface (physical hardware) as good, that the interface is not administratively shut down or looped, and that this interface’s connection is properly clocked. The line protocol being reported as down, however, is usually due to lack of synchronization between the Frame Relay DTE (usually the router) and DCE device (usually the service provider’s switch).

1. This is usually the result of LMI mismatch between the router and the switch.

2. protocol being down is directly related to whether that particular DLCI is active or not.

Other possible reasons for the line protocol to be down are:

• The interface is not sending keepalives (keepalives can be stopped using the no

keepalive interface configuration command).

• The leased line is experiencing trouble such as too much noise.

• May be the problem lies in the other end.

New Member

Re: Error message: Line protocol is down.

Also do loop tests and confirm there is no link problems in the line

Check LMI type.


New Member

Re: Error message: Line protocol is down.

Do you get 'up up' if you set the encapsulation back to HDLC? If not, it may be something as simple as not providing a clock on the (layer 1) dce end of the cable.

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