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Re: dumb question posted 09/10/2001
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You're welcome. It should work on your laptop because the actual break signal
comes from the router in response to recieving the "CNTR-SHIFT-6, B". Some
terminal emulators have an option to either handle ctrl-keys locally (<ctrl,c> =
copy, <ctrl,x> = cut, <ctlr,v> = paste, etc.) or send the cntrl char. I've seen
some terminal emulators that seem to get confused on this -- even if you set it
one way, it still does it the other way. Also, sometimes the up arrow and down
arrow keys don't work (need to use <ctrl, p>, and <ctrl, n>).

Another interesting one is <ctrl, v> -- it tells the cisco that the next
character is to be taken literally. For example to enter a "?" into an AS-path
filter regular expression you would type: "<ctrl,v>, ?" (if you just type: "?"
you will get the online help).


kym blair wrote:

> Jon, thanks for posting this very informative description.  I've always had
> a hard time with BREAK in Hyperterm even after reading and reading the Cisco
> webpages on this topic.  Because of your description, I tried "CNTR-SHIFT-6,
> B" and it worked.  I'll try on some laptops at work tomorrow.  You've really
> cleared up the mystery.  Kym
>
> >From: jonatale@xxxxxxxxxxxxx
> >Reply-To: jonatale@xxxxxxxxxxxxx
> >To: Ademola Osindero <ademolaosindero@xxxxxxxxx>
> >CC: David Morton <David.Morton@xxxxxxxxxxxxxxxxxxxxxxxxxx>,        "'Peter
> >Farkas'" <pfarkas@xxxxxxxxx>,        Alex Hsieh <ccie21@xxxxxxxxxxx>,
> >ccielab@xxxxxxxxxxxxxx
> >Subject: Re: dumb question
> >Date: Sat, 08 Sep 2001 23:14:54 -0700
> >
> >The shftt-cntrl-6 = <ctlr,^> = 0x1E = 30 = ASCII Record Separator character
> >(note that the crtl key basically subtracts 64 from the [upper case
> >version] of
> >the char but could be keyboard type dependent)  is the default escape char
> >on a
> >cisco.  The esc char tells the communication device that the next char will
> >represent a command for itself, so the communication device will not pass
> >either char. The list of commands (vendor dependent), *I think*, is given
> >by
> >"shftt-cntrl-6, ?" - this was in an email on this list about 4 weeks ago.
> >Just
> >like in Bisync and in SLIP, if the escape char needs to be sent thru then
> >two
> >esc chars are sent. This is why if you daisy chain ciscos together (term to
> >con
> >of first, aux of first to con of second, aux of second to con of third,
> >etc.)
> >and reverse telnet to each one sequentially then you must enter
> >"<ctlr,^>,x" to
> >get back to the the first cisco, "<ctlr,^>,<ctlr,^>,x" to get back to the
> >second cisco, "<ctlr,^>,<ctlr,^>,<ctlr,^>,<ctlr,^>,x" to get back to the
> >third
> >cisco,
> >"<ctlr,^>,<ctlr,^>,<ctlr,^>,<ctlr,^><ctlr,^>,<ctlr,^>,<ctlr,^>,<ctlr,^>,x"
> >to
> >get back to the forth cisco, etc.
> >
> >The escape SEQUENCE is the command that tells the communication device to
> >terminate the character stream locally rather than passing the character
> >stream
> >thru, on a cisco it is represented by "<ctlr,^>, x".
> >
> >The break SEQUENCE is the command that tells the communication device to
> >send a
> >break SIGNAL instead of passing the character stream thru, on a cisco it is
> >represented by "<ctlr,^>, b".
> >
> >The break SIGNAL is a momentary raising of the voltage to +. It is not an
> >ASCII
> >character. It is similar to toggling DTE, but many terminal use only 3 pins
> >(TX, RX, GND) so this is a way to send a [very (OSI layer 1] low level
> >signal.
> >
> >When the cisco receives a break signal while it is booting, it stops
> >booting
> >and falls back to ROMMON mode, which is a limited OS typically contained in
> >hardware (on a chip). The reason it is in hardware is because hardware is
> >less
> >likely to get corrupted so if the software gets corrupted the box can
> >usually
> >at least get to the ROMMON where the software can be fixed.
> >
> >The config-register can be set such that when the cisco receives a break
> >signal
> >AT ANY TIME, it falls back to ROMMON mode.
> >
> >There is no way, to my knowledge, to force the cisco to fall back to ROMMON
> >mode at any time via telnet. This is probably for security reasons.
> >
> >In conclusion, maybe if:
> >  set config register such that it will always fall back to ROMMON mode
> >when
> >receives a break signal
> >  (obviously, must already be booted to telnet in)
> >  connect aux to con
> >  telnet to port 2001
> >then you can get to ROMMON via telnet (my guesses are are that your session
> >will drop because ROMMON does not support telnet server)
> >
> >PS
> >There is a telnet break - but how to send it depend on your telnet client,
> >and
> >what it does - I don't know. I know cisco does have a command(s) dealing
> >with
> >this.
> >
> >
> >
> >
> >
> >config reg
> >
> >Ademola Osindero wrote:
> >
> > > Connect from the console.
> > >
> > > --- David Morton
> > > <David.Morton@xxxxxxxxxxxxxxxxxxxxxxxxxx> wrote:
> > > > I hate to admit that I'm stumped on this one too.
> > > > I'm connecting to my
> > > > routers via Win2K telnet to a 2509 acting as a
> > > > terminal server.
> > > >
> > > > I've tried all the key combinations in the link
> > > > below, but have no luck.
> > > > Some combos do cause the ############ to shift to a
> > > > new line, but the IOS
> > > > load continues.
> > > >
> > > > If I directly connect via a console cable, it works
> > > > flawlessly. Obviously
> > > > I'm missing something simple, so be kind :>
> > > >
> > > > Take care
> > > >
> > > > David
> > > >
> > > > David Morton CCNP, CCDP
> > > > Principal Engineer
> > > > O p e n  T e l e c o m m u n i c a t i o n s
> > > > davidm@xxxxxxxxxx
> > > >
> > > >
> > > > -----Original Message-----
> > > > From: Peter Farkas [mailto:pfarkas@xxxxxxxxx]
> > > > Sent: Thursday, September 06, 2001 1:43 AM
> > > > To: Alex Hsieh
> > > > Cc: ccielab@xxxxxxxxxxxxxx
> > > > Subject: Re: dumb question
> > > >
> > > >
> > > > Here is the page on cco about it:
> > > >
> > > > http://www.cisco.com/warp/public/701/61.html
> > > >
> > > >
> > > > Alex Hsieh wrote:
> > > > >
> > > > > hi group
> > > > >
> > > > >      I know this is a silly question,please be
> > > > patient with me.Can anyone
> > > > > please tell me what "break sequence" means when
> > > > you want to change config
> > > > > register?Thanks for help.
> > > > >
> > > > >
> > > >
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