Port Traffic Controls
Guaranteed Minimum Bandwidth (GMB) on the Series 5300xl Switches
14-24
Syntax: [ no ] int < port-list > bandwidth-min output (Continued)
[ < queue1% > < queue2% > < queue3% > < queue4% >]
For ports in < port-list >, specifies the minimum outbound
bandwidth as a percent of the total bandwidth for each
outbound queue. The queues receive service in descending
order of priority. You must specify a bandwidth percent
value for all four queues, and the sum of the bandwidth
percentages must not exceed 100%. (0 is a value for a queue
percentage setting. See the Note, below.) Configuring a
total of less than 100% across the four queues results in
unallocated bandwidth that remains harmlessly unused
unless a given queue becomes oversubscribed. In this case,
the unallocated bandwidth is apportioned to
oversubscribed queues in descending order of priority. For
example, if you configure a minimum of 10% for queues
1 - 3, and 0% for queue 4, then the unallocated bandwidth
will be available to all four queues in the following
prioritized order:
1. Queue 4 (high priority)
2. Queue 3 (medium priority)
3. Queue 2 (normal priority)
4. Queue 1 (low priority)
A setting of 0 (zero %) on a queue means that no bandwidth
minimum is specifically reserved for that queue for each
of the ports in < port-list >. Also, there is no benefit to setting
the high-priority queue (queue 4) to 0 (zero) unless you
want the medium queue (queue 3) to be able to support
traffic bursts above its guaranteed minimum.
Notes: Configuring 0% for a queue can result in that
queue being starved if any higher queue becomes over
subscribed and is then given all unused bandwidth.
The switch applies the bandwidth calculation to the link
speed the port is currently using. For example, if a 10/
100 Mbs port negotiates to 10 Mbps on the link, then it
bases its GMB calculations on 10 Mbps; not 100 Mbps.
Use show bandwidth output < port-list > to display the
current GMB configuration. (The show config and show
running commands do not include GMB configuration
data.)