[mrtg] Re: bandwidth statements on Cisco

Jay Hennigan jay at west.net
Wed Sep 29 06:33:31 MEST 1999

On Tue, 28 Sep 1999, Meena Chockalingam wrote:

> Cisco allows bandwidth statements to set the correct clocking speed on the 
> serial interfaces. Does this affect the ifSpeed variable?

Not exactly.  In most cases, the "bandwidth" statement is strictly 
informational for the Cisco config, just like the "description" line.

Serial interfaces if DTE (which most are) derive the clock speed from
the attached CSU.  If you're running back-to-back serial interfaces then
you need a special cable, and on the CDE side need to specify the interface
command 'clock rate nnnnnn'.

Some routing protocols (EIGRP) will use the specified bandwidth parameter 
as part of the metric for determining the best route.  

> If it does not, how does the ifSpeed variable get populated with a value?

If you use the '--vendor' option in cfgmaker, MRTG will import the bandwidth
statement from the interface into the config.  It may do this even without
the '--vendor' flag.  If there is no bandwidth statement, MRTG gets a default
from the router of 1.544Mb/s for serial interfaces.  Note that '--vendor'
is literal.  You type the word, 'vendor'.  At first I was typing '--cisco'
figuring that it wanted the name of the vendor there.  Not so.

Jay Hennigan  -  Network Administration  -  jay at west.net 
NetLojix Communications, Inc.  NASDAQ: NETX  -  http://www.netlojix.com/
WestNet:  Connecting you to the planet.  805 884-6323 

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