[c-nsp] PPP encapsulation triggering LOF on DS3?

[Vincent De Keyzer]

I also have a similar problem, but it's slightly different:
* access router is 7500 with PA-2E3
* CPE is 7200 with PA-E3
* in between there are two transmission links that are chained: one E3 over
SDH, and one E3 wireless link
* everything works fine as long as CPE does not reload
* when CPE reload, access router sees a LOF and line protocol stays down
* disconnecting and reconnecting the coaxes on any of the routers, or
setting then removing a loop on the SDH section (in any direction) fixes the
problem

I will try to see if going to HDLC or enabling scrambling helps.

Thanks guys 

Vincent


> -----Original Message-----
> From: cisco-nsp-bounces at puck.nether.net [mailto:cisco-nsp-
> bounces at puck.nether.net] On Behalf Of Vinny Abello
> Sent: vendredi 19 novembre 2004 3:40
> To: Kevin Graham
> Cc: cisco-nsp
> Subject: Re: [c-nsp] PPP encapsulation triggering LOF on DS3?
> 
> That's interesting, as we have a DS3 with a certain provider running into
> a
> 7206VXR PA-T3, etc.... and the provider said their default encapsulation
> type is PPP. We turned up the line and it looked ok and we could ping
> across it no problem... as soon as we turned up BGP and had traffic
> flowing
> over it, it seemed almost like certain traffic was being blocked but not
> all of it. After troubleshooting for quite some time, I suggested they
> enable scrambling on the circuit. Once scrambling was enabled, everything
> was pristine. We never tried HDLC as I don't think it would have made a
> difference, but that's interesting to hear. All of our clear channel DS3's
> on our network run with scrambling enabled (on our backbone and such). I
> believe one is HDLC actually, but most are PPP but they all have
> scrambling
> enabled. I've never had good experiences without scrambling enabled but it
> could just be my particular situations.
> 
> At 08:46 PM 11/18/2004, Kevin Graham wrote:
> >Just ran into a problem that I'm absolutely clueless on that I was
> >hoping someone could share some insight..
> >
> >On a clear-channel DS3 terminating directly onto Cisco DS3 interfaces
> >on both ends (PA-T3 on a 7200 and some GSR LC on the other) w/ PPP
> >encapsulation link that had been good for several months went down.
> >Interface would bounce down and then back up every 20s or so with an
> >rxLOF, though line proto would never go up with a pile of CRC's on the
> >7200 side (GSR side was always up/down with no errors). clockrate was
> >osillating some though always in the 44M range.
> >
> >Loopbacks either way all came back clean and telco PM also looked
> >good. However, whenever the link was normalized, the troublesome
> >behavior would come back. After a round of loopbacks (of course using
> >HDLC), both ends noticed that the link was running perfectly. Going
> >back to PPP would cause the same problems..Went ahead and left it at
> >HDLC and has been running fine.
> >
> >So... Is anyone aware of WTF could be going on that would cause PPP
> >encapsulation to trigger a consistent LOF condition whereas HDLC does
> >not? The only thing that comes to mind at all is perhaps scrambling
> >(which is disabled), though as mentioned the line has been stable for
> >months....
> >
> >Thanks.
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> 
> 
> Vinny Abello
> Network Engineer
> Server Management
> vinny at tellurian.com
> (973)300-9211 x 125
> (973)940-6125 (Direct)
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> 
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> 
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