Excellent explanation Chuck !!
I've never thought of it that way .
I forgot (using the frame relay example) that the total of all the lines'
CIR's together should be equal to the line speed at your primary interface .
for example ----16k---}
----16k---}====serial0(64k)(((Router))
---16k---}
---16k---}
But now I have a serial line (hdlc) with a isdn as backup . Now if the
serial goes down then the isdn should kick in . Why would that bandwidth 8
then still be in there ? If the serial comes up again then the isdn goes
down .
I mean you can either use the dial backup command or floating static or
something like that . In essence , the cost (routerwise to determine the
path) factor is sorted out .
I agree that if there is money involved and you pay for the amount of data
that flows , its another story .
But under perfectly normal circumstances why would one do that ?
If you configure an isdn line and you do the bandwidth 8 statement , do you
only use 8k of that whole 64k line ? Or do you use streams of 8k on that 64k
line ?
I'm asking because I am not sure . Thanx for the patience !
Cheers
Olden
-----Original Message-----
From: Chuck Larrieu [mailto:[EMAIL PROTECTED]]
Sent: Saturday, July 29, 2000 5:33 PM
To: Olden Pieterse; [EMAIL PROTECTED]
Subject: RE: what i just saw...
Let's look at what is happening
With frame relay, you have a port speed and a committed information rate. If
the port speed is 128K, and the CIR is 16K, the following will happen when
you transmit data.
1) data will pass into the frame relay network at the full port speed.
2) The frame relay cloud ingress router marks all frames in excess of the
CIR as discard eligible.
3) If bandwidth is available, frames travel through the frame relay network
at whatever speed that link is provisioned for. If not, the frames are
dropped.
Several routing protocols - i.e. OSPF, EIGRP, IGRP - use "cost" as part of
the means of path determination. From a design standpoint one might have a
reason or two for preferring some paths over others. Let's say that I have
some servers in a co-location facility, and the co-lo charges for data
passed into and out of that facility, based upon fee plus charge for data
over a certain threshold on the line. I have my primary path in. I want all
traffic to use that path. But I want a backup path in case the primary
fails. My primary is frame relay with a port speed of 1.54 and a CIR of
500K. My backup is a frame relay with a port speed of 1.54 but a CIR of 0.
If the router sees two paths, both costing the same (using default settings,
it's 64 for OSPF, isn't it?) Depending upon the routing protocol, I could
end up sending traffic over the circuit with the 0 CIR and incur substantial
fees. So I use the bandwidth command to influence the router to prefer the
primary path over the secondary.
I'm sure there are many other situations in which one might want to do
similar things.
HTH
Chuck
-----Original Message-----
From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED]] On Behalf Of
Olden Pieterse
Sent: Saturday, July 29, 2000 12:50 AM
To: '[EMAIL PROTECTED]'
Subject: what i just saw...
I am in like Frame Relay stuff ,like in knee ,no hip deep in this fecn becns
AND what do I see ?
no not the the wolf in little red riding hood !!
BUT
and I quote (thank you Cisco) "Remember ,the total bandwidth is derived from
what was configured using the bandwidth command ,or the default which is
1.544 Mbps "
So you want to tell me that guys is wasting precious bandwidth ?
Please let me know when I can take the ice-cream off my forehead (if I had
one in the first place !)
...its ok you can smile now !
Cheers
Olden Pieterse
MCP , CCNA , BCMSN , BSCN , BCRAN
Brainbench Certified CISCO Network Implementation Specialist
Technical Consultant
Mobile : +27 82 410 8621
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