EIGRP bandwidth control over Serial Subinterfaces

[ravindra Krishna]

Hi All,

Lets consider a t1 link on a routers serial interface. The link is having 4 PVC. 2 are on s1/0.1 and one on s1/0.2 and one more on the s1/0.3. If i issue no command of bandwidth control, then how the EIGRP is going to use this BW for each PVC on serial S1/0.1 and on S1/0.2 or S1/0.3.

I could understand under defaults, each interface would have around (1544/3=) 515 Kbps. But how about the 2 PVC existing on the Serial S1/0.1.

Documentation ref will also be helpful.

Cheers!

Ravi

[vmiller]

Bandwidth values for physical interfaces are set at statrup time (based

on the hardware)

for subinterfaces (logical) youset it yourself.

[ravindra Krishna]

Hi,

As said earlier I have not specified any BW command. Please let us know how the BW is distributed on default conditions. A ref document will also be helpful.

Cheers!

Ravi

[vmiller]

There are default bandwidth definitions for all interfaces, its nothing you set. For serial, the default is t-1 speeds

bandwidth

To set a bandwidth value for an interface, use the bandwidth interface configuration command. Use the no form of this command to restore the default values.

bandwidth kilobits
no  bandwidth

Syntax Description

kilobits

Intended bandwidth in kilobits per  second. For a full bandwidth DS3, enter the value 44736.

Default

Default bandwidth values are set during startup and can be  displayed with the EXEC command show interfaces.

http://www.cisco.com/en/US/docs/ios/11_0/router/command/reference/rinterfc.html#wp1396

Its an old reference.

[ravindra Krishna]

Lets consider a t1 link on a routers serial interface. The link is having 4 PVC. 2 are on s1/0.1 and one on s1/0.2 and one more on the s1/0.3. If i issue no command of bandwidth control, then how the EIGRP is going to use this BW for each PVC on serial S1/0.1 and on S1/0.2 or S1/0.3.

I could understand under defaults, each interface would have around (1544/3=) 515 Kbps. But how about the 2 PVC existing on the Serial S1/0.1.

I think I got the answer:

Since, we have not specified any BW command the default is 1544so for subinterfaces with one PVC, each would you use around (1544*50%=)772Kbps for EIGRP traffic.

And for the subinterface with 2 PVC it would be round (1544*(1/2)*50%=)386 Kbps.

Hope now this is absolutely right!

Below are ref links:

http://www.cisco.com/en/US/tech/tk365/technologies_tech_note09186a0080094063.shtml#nbma