Cisco Support Community
Showing results for 
Search instead for 
Did you mean: 

Welcome to Cisco Support Community. We would love to have your feedback.

For an introduction to the new site, click here. If you'd prefer to explore, try our test area to get started. And see here for current known issues.

New Member

real bandwidth

CG2RT6021#sh interfaces atm 5/0.1

ATM5/0.1 is up, line protocol is up


Description: intranet atm 34/45M to KTCRT9041 ATM2/0.1 VPI/VCI 1/41 AT&T#08011 214935

Internet address is

MTU 4470 bytes, BW 34000 Kbit, DLY 190 usec,

reliability 255/255, txload 12/255, rxload 26/255

Encapsulation ATM

1384464238 packets input, 14944437949 cells, 677337513789 bytes

1231688251 packets output, 6988749163 cells, 297241302333 bytes

1 OAM cells input, 1 OAM cells output

AAL5 CRC errors : 124

AAL5 SAR Timeouts : 0

AAL5 Oversized SDUs : 0

Last clearing of "show interface" counters never

In the output shows BW 34000 kbits, is this because I put bandwidth 34000 on the interface? Currently there is a bandwidth 34000 command on my interface, what if i dont put the bandwidth command, what will be the effect? can I still get the actual bandwidth? pls. help////thanks


Re: real bandwidth


Bandwidth command doesnt have any relation on the actual bandwidth committed by your SP to you.

Its basically used by the routing protocols (like eigrp,ospf)for the best path computations.

As well as to compute the load conditions getting displayed there as txload/rxload.

Though you configure less amount of bandwidth under the interface when compared to the offered bandwidth you will still get the offered bandwidth from the sp.

But its better to have the exact bandwidth offered by the SP to be configured under the interface.


New Member

Re: real bandwidth


Thanks for the reply, just a follow up, say my SP assigned me a 45M and I put in my interface bandwidth 10000, whats the effect of this? will this means that im in control of assigning bw in my interface, what if I dont have any idea of how much bw assigned to my interface and I put bw beyond what is assigned to me, is there any effect? Is there anyway to know the offered bw by my SP? So whats the use of assigning less bw under the interface?

Re: real bandwidth


As i have clearly mentioned in my previous post there wont be any effect on the performance of the link connected to the interface.

You still can pump the traffic based on the bandwidth assigned/configured by your SP though you have lesser or higher value configured under the interface.

As you have mentioned you dont have any control using bandwidth command untill unless you are running any routing protocol which takes/considers the bandwidth parameter while doing the best path calculation.

Assigning lesser bandwidth makes the routing protocol to defer sending traffic through this link and prefer some other path/link instead.

Its just the viceversa phenomena with the other way around.


Re: real bandwidth

You could try the following commands:

"show run interface ATM5/0.1" // to see config of sub-if

"show atm vc" (or "show atm pvc") // to see what VCs you have and brief cfg info

You could try "show atm ? " and explore a bit, though the config

under ATM5/0.1, under pvc x/y should be enough to see what's going on.

What you configure under the sub-if ATM5/0.1 , under the pvc 1/41 submode

(if 1/41 in the description is correct, otherwise what you have under pvc x/y holds)

is what will greatly determine the amount of bandwidth you will get

(and not the bandwidth cmd, which has already been stated).

In general, you cannot get more from your upstream than they have configured to offer you.

Your VC type (ubr, vbr, etc) should much theirs,

and the values of parameters (PCR,SCR,MBS, etc.) should also much.

If you configure (under pvc x/y ) your part for more, and attempt to sent more,

the upstream will probably drop it, and you might get poor performance for certain application types.

If you configure (under pvc x/y ) less, you risk dropping traffic on your side

although they are willing to send it towards you, which is also bad.

Actual behavior will depend on many things (e.g. VC type, ATM network load).

I suppose somebody had the values and the cfg negotiated with your ISP when the VC was initially set up.

In any case, you should be in touch with your ISP to update the values (under pvc x/y )

whenever there is a change in the traffic contract.