What's the function of the clock rate command? the bandwidth command?

[Panther007]

I am trying to find out what does the clock rate command do?
Is it to define the bandwidth of a serial connection?
And what is bandwidth command.
How does bandwidth command compare to the clock rate command?

That's four questions in one...hope you'll forgive my greediness

Thanks

 

[RouterGod]

Well I'll start by answering the first of your four questions, Clockrate command. This command simply sets the Serial interface clockrate in BPS (bits per second). It is only applicable on a serial interface. In most instances the service provider sets this speed, you need just match it. This has nothing to do with bandwidth per se. The bandwidth is preset by the service provider. Clockrate merely allows the routers or DCE equipment to communicate properly. In my experience you will not get a successfull link if these are mismatched.

As far as the bandwidth command is concerned, this is simply a spoof number. It doesn't actually change the bandwidth. It is commonly used to adjust metrics and convey line properties to other protocols that can use this information.

I know that four questions and only two answers, so ask me to clarify or expand if needed.

Don Regards,

Don Wolf

 

[Panther007]

So, I assume that the bandwidth command is just for maintaining "cost" among the routers for paths and etc..

The clockrate on the other hand is just a physical setting for the serial port to be able to handle different type of load and has nothing to do with actually setting up the speed.

Is that right??

 

[RouterGod]

That's correct. Not all protocols have the ability to change it's metric, this allows a little more fine tuning. Regards,

Don Wolf

 

[norsyam21]

Hi.

Clock rate is for router connection which is DCE eg. back-to-back. Bandwidth is for dynamic routing calculation such as IGRP, OSPF and so on.

 

[Ken2001]

The clock rate command is used to match the clocks of the receiver/transmitter on the remote router and local router.
Basically, the two routers would have to synchronize their clocks to each other so that they could decode the packets entering their interfaces. If the clock rates do not match, theres no way for the routers to decode the individual bits in the packets.

The bandwidth command however is needed to manually assign a bandwidth value on the interface. By default, the routers do not have any mechanism to detect the actual bandwith of a serial line and its is set to a default value of 1.544 MBPs. Therefore if you have one 64K serial line and another T1 line on the same router, if you dont manually change the bandwidth value on the 64K serial line, the router will treat both as T1 lines. Its a method to tell the router that it is a slower link so that actual metrics can be computed accurately.