You have hit on the most difficult thing to keep straight for the BCRAN test.
First my ramblings:
I am probably wrong but it seems that somewhere around 10.3 code the IOS
command
"structures" were changed. For example Async-Groups are very similar in
function to the Dialer Groups. For some reason instead of expanding the
capabilities for the old commands they re-wrote them and left the old stuff
in
the IOS for backward compatibility. So now there is a odd mix of commands
which
do almost the same thing; makes it very confusing.
TO ALL: PLEASE CORRECT ME IF I AM OFF MY NUT ;-}
Lines: TTY (VTY is a little different)
The Line is like a software driver for your modem.
Lines correspond to the software that directly controls the Physical Layer of
the ports. "Sh Line" will indicate the relation between line # and physical
port #. Line commands control the physical aspects of the line. Many of
the
line commands are obviously meant to control physical aspects of the ports.
Others like autoselect, autocommand, login, are not so obvious; but really
direct data received on the port to other control functions. Example
autoselect
PPP tells the TTY port to read the characters as part of a PPP frame. You
don't
have to do this for other type interfaces on a router becasue the Physical
characteristics are hardcoded into the port.
Async Int:
The Async Int are like the protocol drivers on your PC.
It binds the protocol services (IP, IPX, etc) to a line. Async int defines
the
layer 2 (PPP or SLIP etc..) encapsulation and the layer 3 protocols.
*note if dialer interfaces or Aysnc-groups are used you may see commands
duplicated between the async interfaces and the dialer Int/Async Group.
Depending on the situation inbound call, outboud, DDR etc,; only one of the
two
duplicated commands are looked at by the router. Also a confusing issue :}
Dialer interfaces and Async-Groups:
They tie several Async ports together to allow you to access the async/lines
in
a flexible manner.
It sounds that your are doing fine; It is confusing but sound like you have a
pretty fair grasp on it. If you do start to "Truly Understand" this stuff;
you
need to take a LONG Vacation..
DaveC
Albert Lu wrote:
>
> Hello Group,
>
> I'm getting a little confused about configuring Async, Dialers and Lines.
>
> I've been reading the BCRAN book and looking at the sample config
>
http://www.cisco.com/warp/public/779/smbiz/service/configs/async/async_ip_st
> atic_aux.htm
>
> I'm not sure how to configure 'Line' for modems. There are a few ways of
> doing it that I have seen, using 'modem autoconfigure discovery', setting
> speed/stopbits/flowcontrol, and specifying a modem type from the modemcap.
> I'm confused by the various ways, and would like to know what really is
> necessary.
>
> Secondly, the relation between Lines and Async interfaces are abit blurry
> for me as well. From my knowledge, Lines are used to configure modem
related
> stuff and Async are used to config higher level things such as ppp and
> dialer. Am I close?
>
> Finally, I see in the config from the Cisco site that they use an Async
> interface and a Dialer interface. I was trying to configure the Async
> interface and putting the 'dial map' command in the Async interface, and
now
> I see it in the Dialer interface. Isn't Dialer interfaces only necessary if
> you want to bundle multiple Async/BRI interfaces together into one logical
> Dialer interface?
>
> I must say that Line/Async/Dialer configs are the most longest, confusing
> and least intituitive for something this simple. Most of the time I
remember
> most of the configs that are necessary, but sometimes miss out on a few
> which makes it not work.
>
> Anyone have any tips they wish to share to help remember, or is it just
> something I will get a hang of after awhile?
>
> Thanks
>
> Albert
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