Bandwidth allocation per port on 3750G Catalyst switch

Unanswered Question
Aug 26th, 2007

Is it possible to allocate a specified percentage of bandwidth to a protocol e.g. FTP on 1 port on a catalyst 3750G switch? I would like to ensure that FTP traffic does not use more than 50% on the bandwidth on a specific siwtch port.

Many thanks

I have this problem too.
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Joseph W. Doherty Mon, 08/27/2007 - 03:25

You can police (or rate limit) inbound port traffic. Don't believe you can actually specify, directly, 50%, but you could, for example, specify that FTP is limited to 500 Mbps on a gig port.

You could also shape egress FTP traffic to fixed percentage (using "shaped mode"). (You can't shape FTP directly, you shape using the egress queues, so if you only place FTP in only one queue, then you directly control it.)

There are some slight capability feature differences between the software versions on the switch, for instance whether you only want to police at the physical port or at the SVI.

See the "Configuring QoS" section of the configuration guide for details, e.g.


Instead of restricting FTP's share of the bandwidth, another approach might be to place FTP in an egress queue with a low % allocation using "shared mode". This helps to keep traffic like FTP from adversely impacting other traffic, but allows it to use all available excess bandwidth.

davidbuit Thu, 09/13/2007 - 16:10

Please see the config below. I want to restrict abound traffic from my LAN on port 8989 on a cisco 3560G switch.

Does this look correct? Are there any additional implications of enabling mls qos on the switch? Will this affect any other interfaces besides Gig 0/11?

Thank you!

mls qos


access-list 100 permit tcp any eq 8989


class-map match-all c_markdscp

match access-group 100


policy-map p_markdscp

class c_markdscp

set dscp 60


mls qos srr-queue output dscp-map queue 2 threshold 3 0

mls qos queue-set output 1 buffers 10 60 10 20

interface GigabitEthernet0/11

srr-queue bandwidth shape 0 0 0 9



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