Clockrate vs Bandwidth/Speed

iworms

When I connect two routers back-to-back with a serial cable, does it matter what clockrate I set on the DCE side? No matter what clockrate I use, sh int s0 always shows BW 1544 Kbit.

On the other hand, the bandwidth 102400 command can change an interface's apparent bandwidth, but this can be set arbitrarily and does not reflect the physical speed.

dynamik

If I remember right, the bandwidth is used for letting routing protocols know what the speed is, so they can make routing decisions based on that. I don't think it has anything to do with actually configuring an interface.

tiersten

The bandwidth command is to tell the routing protocols how fast your link is. The clockrate command however will affect how fast the link is because you can't transfer faster than what the clockrate is. As for why there it is split into two, you may have fractional links that are throttled at the other end. Your interface still runs at the full speed but you just can't push anything more than what it will throttle to.

If it is for your own test lab then just use 64000. It'll be fast enough to do your testing. You can crank it up way past 1mbps but there isn't any point and you may start getting issues with the quality of your cables and/or hardware.

Plazma

The bandwidth command is only used to ensure a correct metric is calculated by routing protocol. Clockrate is what you use when you simulate a CSU to send how fast the line can acutally recieve data. By default, a T1 is 1.544Mbps.