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New Member

HDLC not working

Hi Experts,

We have 2 sites interconnected with WAN links. The WAN connectivity is based on Serial P2P links. However the problem that we are facing is that when we configure the HDLC protocol at both ends, the line protocol remains down even though both side routers are Cisco(Cisco 2600 series). We are able to bring the Line Protocol up with the PPP.

Please can someone advise as to what could be the possible reason for the same and suggest some points that we can check.

Many thanks in advance.

  • WAN Routing and Switching
Hall of Fame Super Gold

Re: HDLC not working


that is really strange. You would need to send "show interface" for both routers when either HDLC or PPP is configured, doing "clear counters" in between.

Hall of Fame Super Silver

Re: HDLC not working


I agree with Paolo that this is really strange. Is it possible that one router was configured with no keepalive when it was configured for HDLC? In addition to the request for posting the output of show interface I believe that it would be very helpful if you would post the interface configuration, both when configured as HDLC (and not working) and when configurd as PPP and working.



New Member

Re: HDLC not working


You are of the routers was configured for No Keepalives...however we had taken that command off of the interface and w when we give the "show interface" it say that the keepalive is defaulting to 10 secs. Please advise.

Hall of Fame Super Gold

Re: HDLC not working

Correct, default keepalive 10 seconds.

Please do not change this default and leave keepalive active unless there is a proved reason to change that.

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New Member

Re: HDLC not working


The keepalive part is ok..however the HDLC problem is still persisting. I will try and post the show interface output as soon as possible.

Many thanks for helping.

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