回复: ??: Strange result while ping serial interface

["Yu Ning" <yuning () cndata com>]

Thank you very much for your information. I get that page, and
know it's for debugging reason.

regards,

Yu Ning


-----Original Message-----
From: Blake Fithen <fithen () NetworksPlus com>
To: 'Yu Ning' <yuning () cndata com>; Dumb Kid <dumbkid0 () yahoo com>; nanog-post
<nanog () merit edu>
Date: Thursday, May 11, 2000 10:07 AM
Subject: RE: ??: Strange result while ping serial interface


> > From the Cisco "System Management" document:
>
> http://www.cisco.com/univercd/cc/td/doc/product/software/ssr90/tsc_r90/5401
9
> .htm
>
>
> "Note If the IP version of the ping command is used on a directly connected
> interface, the packet is sent out the interface and should be forwarded
> back to the router from the far end. The time travelled reflects this round
> trip
> route. This feature can be useful for diagnosing serial line problems. By
> placing the local or remote CSU/DSU into loopback mode and "pinging"
> your own interface, you can isolate the problem to the router or leased
> line."
>
> blake
>
>
> > -----Original Message-----
> > From: Yu Ning [SMTP:yuning () cndata com]
> > Sent: Wednesday, May 10, 2000 9:00 PM
> > To: Dumb Kid; nanog-post
> > Subject: ??: Strange result while ping serial interface
> >
> >
> >
> > Hi,
> >
> > But it's obviously inefficient. Is it due to some inability of
> > PPP ? Or can you tell what reason makes the packets a round
> > trip ?
> >
> > Since the router should have the information of its local interface,
> > why should it always send packets out, the get it back ?
> >
> > regards,
> >
> > Yu Ning
> >
> > -----Original Message-----
> > From: Dumb Kid <dumbkid0 () yahoo com>
> > To: Yu Ning <yuning () cndata com>; nanog-post <nanog () merit edu>
> > Date: Thursday, May 11, 2000 9:45 AM
> > Subject: Re: Strange result while ping serial interface
> >
> >
> > > Yeah , it's normal. The packet actually travels to the
> > > other end of the router over the serial and back.
> > > That's why the response time is doubled.
> > >
> > >
> > >
> > > --- Yu Ning <yuning () cndata com> wrote:
> > > > Hi nanog,
> > > >
> > > > Strange thing happens everyday. When I were
> > > > troubleshooting yestoday,
> > > > I found a ping to my local serial interface (no
> > > > matter it's 155M POS,
> > > > or 2M Serial interface) takes nearly twice delay
> > > > compared with a ping
> > > > to the remote side of the serial interrface ! When I
> > > > trace to my local
> > > > serial interface, I got the first hop to the remote
> > > > end, then second
> > > > hop back to my local interface !
> > > >
> > > > For example, 202.97.2.1 is local serial interface,
> > > > while 2.2 is remote
> > > > side. A trace on 2.1 to 2.1 first go to 2.2, then
> > > > back to 2.1. And this
> > > > situation can be verified on both side.
> > > >
> > > > Have you ever seen this situation ? Is it due to our
> > > > misconfiguration?
> > > > or it's sheerly a mis-display of result in Cisco box
> > > > (can't believe it)
> > > >
> > > > The background is: we're using ISIS as IGP, and
> > > > utilized level-1/2 link.
> > > >
> > > > thanks for any input.
> > > >
> > > > regards,
> > > >
> > > > Yu Ning
> > > > -------------------------------------------
> > > > (Mr.) Yu(2) Ning(2)
> > > > ChinaNet Backbone Operation
> > > > Networking Dep.,Datacom Bureau
> > > > China Telecom.,Beijing(100088),P.R.C
> > > > +86-10-66418121/66418122/66418123(fax)
> > > > -------------------------------------------
> > >
> > >
> > > =====
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