Clockrate Command

Daniel333

Alright, sorry to be bothering you guys so much today. But hey, what I ask today, might help someone tomorrow. I am studying for the CCNA-Intro exam, so the books I have are kind limited. They alll give examples of either setting the clockrate on the DCE at either 64000 or 128000, which seems off to me. Should be we setting that much higher to support the 10Mpbs the router's Serial ports should be supporting?

Where have I gone wrong on this assumption?

Pash

Well yes, if this is a lab or simulation you are trying to test on you could set your speed as much as allowed by your serial port (infact im not sure of the speeds, you could probably find out from the cisco website dependent on several factors). However, most of the examples provided by cisco press and other study vendors will mention 64k and 128k many times because the DCE equipment in real world scenarios usually sits in an ISP centre, because obviously they decide the physical speed of your p2p connection, if the customer were allowed to set the clockrate then....well you get the idea.

mikej412

Most of the time 56k or 64k is chosen because those speeds will work with most Synchronous or Asyncronous Serial ports. 128k may be chosen because that's the max for the async serial port.

Clock rate options for Synchronous Serial port

R2511-2(config-if)#clock rate ?
        Speed (bits per second)
  1200
  2400
  4800
  9600
  19200
  38400
  56000
  64000
  72000
  125000
  148000
  250000
  500000
  800000
  1000000
  1300000
  2000000
  4000000

  <300-4000000>    Choose clockrate from list above

And from an Asynchronous Serial port

R3620-4(config-if)#clock rate ?
        Speed (bits per second)
  300
  1200
  2400
  4800
  9600
  14400
  19200
  28800
  32000
  38400
  56000
  57600
  64000
  72000
  115200
  128000

  <300-4000000>    Choose clockrate from list above

HSSI interfaces may run up to 52Mbps -- but I don't have any in my home lab.