From: thomas larus (tlarus@xxxxxxx)
Date: Sat Apr 06 2002 - 18:32:11 GMT-3
Okay. I think we all know this by now. 1) The clock rate comes from the provid
er, and 2) The bandwidth command is for calculations done by routing protocols.
<p>
I am sorry to sound testy, but could someone just tell me what clock rate he or
she uses when they want the interface to carry 1.544000 mbps in a lab scenario
. I understand that in the real world it is all different. I think the answ
er is 2000000, but could someone confirm this?
I would like to resolve this simple-seeming question so I can move on to other
, more important questions that I need to resolve, like why does my router igno
re the fact that I configured BC as 8000 and insist that BC is exactly one-thou
sandth of CIR, or, why is it that in a Solie chapter on FRTS, the router decide
d that the interval for the serial interface was 125 ms (which makes sense), bu
t that the interval on the subinterfaces was exactly 12.
I figured that setting my clock rate to 1300000 might have been messing up my "
sh traffic" and "sh frame pvc" figures, and that's why I asked about something
so basic.
>>> Richard Furda <riso@furda.net> 04/06/02 15:29 PM >>>
In real life situations, you have a CSU/DSU providing the clocking
information and the serial interface on a router (being a DTE) would pick
it up.
Rich
On Sat, 6 Apr 2002, thomas larus wrote:
> I know it's not a legal option. That's my point. That's what my screen outp
ut was there to remind us all of. My question is, what clock rate should I use
for an interface that I want to be the same as a real-life T1, that is 1544000.
>
> I have a feeling I am worried about something that simply does not matter. O
therwise, lots of people would have wondeed about this and there would be fifty
ready, right-on-point answers in five minutes, like the old "no peer neighbor-
route" answer that we see every few days in answer to questions about ip ospf d
emand-circuit.
>
>
>
> >>> "Narvaez, Pablo" <Pablo.Narvaez@getronics.com> 04/06/02 14:07 PM >>>
> ummmm If you do a "show controll ser x" do you see that speed as a legal opti
on? ..
>
> R7(config-if)#clock rate 1544000
> Unknown clock rate
> R7(config-if)#clock rate ?
> Speed (bits per second)
> 1200
> 2400
> 4800
> 9600
> 14400
> 19200
> 28800
> 32000
> 38400
> 56000
> 57600
> 64000
> 72000
> 115200
> 125000
> 128000
> 148000
> 192000
> 250000
> 256000
> 384000
> 500000
> 512000
> 768000
> 800000
> 1000000
> 1300000
> 2000000
> 4000000
> 8000000
>
> <300-8000000> Choose clockrate from list above
>
> R7(config-if)#clock rate 2000000
>
>
> cheers,
>
> hockito
>
>
>
>
>
>
> -----Original Message-----
> From: thomas larus [mailto:tlarus@mwc.edu]
> Sent: Sabado, 06 de Abril de 2002 12:58 p.m.
> To: Narvaez, Pablo; ccielab@groupstudy.com
> Subject: Re: RE: What is relation between clockrate and bandwidth?
> Common port speed 1544000, but no clock rate like
>
>
> I understand that the bandwidth command is for routing protocol purposes.
>
> I am sorry that my question seeme to be about the bandwidth command. My ques
tion is about the relations between clock rate and the real bandwidth on the in
terface. I want an interface to be configured to be able to really carry 15440
00 mbps. I should think that to do this I would need to set a clock rate on th
e interface of a that speed or a little bit higher, but that clock rate is not
an option.
> You said:
> " For the lab, you may configure the clockrate as you wish as long as both en
ds match. Just keep in mind that the bw will be responsable for the routing pro
tocol decisions ..."
>
> I just tried to set the clockrate to 1544000,and it would not let me. (We ha
ve all tried to do this at some point, probably.)
>
>
>
> r2613(config-if)#clock rate ?
> Speed (bits per second)
> 1200
> 2400
> 4800
> 9600
> 14400
> 19200
> 28800
> 32000
> 38400
> 56000
> 57600
> 64000
> 72000
> 115200
> 125000
> 128000
> 148000
> 192000
> 250000
> 256000
> 384000
> 500000
> 512000
> 768000
> 800000
> 1000000
> 1300000
> 2000000
> 4000000
> 8000000
>
> <300-4000000> Choose clockrate from list above
>
> r2613(config-if)#clock rate 1544000
> Unknown clock rate
>
>
> So which clock rate setting should I use in a home lab scenario setting whe
re I am trying to emulate a DS-1 of 1544000. Should I use clock rate of 2000000
? What do other folks use? This must be a question lots of you have had, and
found an adequate, and perhaps obvious answer.
>
> Thanks for the excellent point about frame relay multipoint.
>
> Thanks in advance.
>
> Tom Larus
>
>
> >>> "Naraez, Pablo" <Pablo.Narvaez@getronics.com> 04/06/02 13:29 PM >>>
> The bandwith command if for routing protocols only, not for layer1 bandwith/s
peed nor to indicate the rate of the line clock. You may have a clock rate of 6
4000 and bandwith of 128k; most of the time you may want to set both at the sam
e rate in order for the routing protocol to work properly and calculate a "real
" metric for that link,
>
> Some other times you may need to change that bw value, like in multipoint su
b-if with EIGRP not to overflow the low speed PVCs whereas you have to keep the
clockrate according to the provided clock. In a real scenario, most of the tim
es you don't have to deal with clockrates in the interfaces (usually DTEs for e
ndpoints) since you take the clock from internal line and leave that job to the
csu/dsu.
>
> For the lab, you may configure the clockrate as you wish as long as both ends
match. Just keep in mind that the bw will be responsable for the routing proto
col decisions ...
>
> cheers,
>
> hockito
>
>
> -----Original Message-----
> From: thomas larus [mailto:tlarus@mwc.edu]
> Sent: Sabado, 06 de Abril de 2002 12:02 p.m.
> To: ccielab@groupstudy.com
> Subject: What is relation between clockrate and bandwidth? Common port
> speed 1544000, but no clock rate like
>
>
> On my routers, I do not have the option of choosing a clock rate anywhere nea
r 1544000 (the closest rate is 1300000), yet in countless scenarios (like Solie
's) we set the frame relay cir to 1544000. How can we have a port speed of 154
4000 when that is never an option on our routers as a clockspeed.
>
> Could someone explain this.
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