available bandwidth on mppp

Answered Question
Aug 5th, 2009

I have an mppp line with 3 t-1's in the bundle. When I "show int mu1", it says "Available Bandwidth 1 kilobits/sec". how can that be? I do have some qos configured on this inteface too.

I have this problem too.
0 votes
Correct Answer by Istvan_Rabai about 7 years 2 months ago

You're welcome Daryle.

Please rate my post if it was helpful for you.



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Overall Rating: 5 (4 ratings)
Peter Paluch Wed, 08/05/2009 - 13:32


Can you post the configuration of your multilink interface here please?

Best regards,


DARYLE DIANIS Wed, 08/05/2009 - 13:47

Here's the mu1, with a few things x'd out:

interface Multilink1

ip address xxx.xxx.xxx.xxx

no ip route-cache cef

ip route-cache flow

no ip mroute-cache

load-interval 30

delay 3000

no peer neighbor-route

ppp multilink

ppp multilink group 1

service-policy output xxxxxx



Peter Paluch Wed, 08/05/2009 - 13:57


Thank you. Try setting the combined bandwidth using the command bandwidth on the interface. You are using three T1 then configure it as:

bandwidth 4632

Please let us know if this worked. Note that the interface reserves 25% for framing overhead and control traffic, therefore, only 75% of the configured bandwidth is available.

Best regards,


Istvan_Rabai Wed, 08/05/2009 - 16:04

Can you post the configuration of the policy-map you use on the Multilink interface?



DARYLE DIANIS Wed, 08/05/2009 - 16:10

here is the policy map, I think its fairly simple:

policy-map xxxxxxx

class PRECEDENCE5_cmap

set ip precedence 5

priority percent 35

class PRECEDENCE4_cmap

bandwidth percent 25

class PRECEDENCE3_cmap

bandwidth percent 15



Istvan_Rabai Wed, 08/05/2009 - 16:32

The total available bandwidth is 100% without configuring any policy-map on the interface.

In your configuration, you allocated 75% of the available bandwidth to several traffic types. Remains 25%.

Although in your configuration it is not apparent, there is a class-default queue within your policy-map. By default it is allocated 25% of the available bandwidth.

You can check it using the "show policy-map interface multilink1" command.

Altogether, if you add up all the bandwidths you configured + this 25% bandwidth, all the 100% bandwidth is used up: 35%+25%+15%+25% = 100%.

This is why you get the "Available bandwidth 1kbps" message, which is I think may be just a rounding calculation error in the software.

The Available bandwidth message simply indicates how much of the interface bandwidth is still available for allocation to additional traffic types within your policy-map.

It does NOT mean you don't have the bandwidth of the 3 T1 lines.

Use the show interface multilink1 command to look at the bandwidth of the interface (and it will also display the available bandwidth for allocation to additional traffic types).

You should use the "bandwidth" command under the multilink interface to set the real bandwidth (if it isn't already set automatically to the right number) so QoS functions correctly.



DARYLE DIANIS Wed, 08/05/2009 - 16:40

thanks for a great explanation. I'll keep the qos config in mind in the future.



Correct Answer
Istvan_Rabai Wed, 08/05/2009 - 16:43

You're welcome Daryle.

Please rate my post if it was helpful for you.




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