You are not assigning 70% of the bandwidth because you are using the
You are not reserving or dedicating the bandwidth you assign. If a class is not using all its bandwidth, other classes can use it, too. The default class gets to use any unreserved bandwidth that is not used. It could use up to 100% of the bandwidth, as can any of the classes, if it is not reserved. The
bandwidth percent command doesn't exclusively reserve bandwidth.
Cisco has a paper describing how this works:
How Is Unused Bandwidth Allocated?
This section explains how the queueing system distributes any
remaining bandwidth. Here is how the Class-Based Weighted Fair
Queueing Feature Overview describes the allocation mechanism: "If
excess bandwidth is available, the excess bandwidth is divided amongst
the traffic classes in proportion to their configured bandwidths. If
not all of the bandwidth is allocated, the remaining bandwidth is
proportionally allocated among the classes, based on their configured
bandwidth." Let's look at two examples.
In the first example, policy-map foo guarantees 30 percent of the
bandwidth to class bar and 60 percent of the bandwidth to class baz.
bandwidth percent 30
bandwidth percent 60
If you apply this policy to a 1 Mbps link, it means that 300 kbps is
guaranteed to class bar, and 600 kbps is guaranteed to class baz.
Importantly, 100 kbps is leftover for class-default. If class-default
does not need it, the unused 100 kbps is available for use by class
bar and class baz. If both classes need the bandwidth, they share it
in proportion to the configured rates. In this configuration, the
sharing ratio is 30:60 or 1:2.