Bandwidth Management

[quintin]

Is there a way to either use SNMP or some other menas of management to limit the bandwidth on a 3550 switch port based on time of day? I want to allow a port used for disaster recovery and backups full bandwitch at night but limit it during the day when it will impact other users.

[mheusinger]

Hi,

you could combine a policer with a time-based access-list describing the traffic to be policed. Just make sure you use ntp as well, otherwise after a reload your 3550 defines day and night through local system clock not in sync with the rest of the world ... which could be desastrous.

Check the following links for configuration options:

"Understanding QoS Policing and Marking on the Catalyst 3550"

http://www.cisco.com/en/US/products/hw/switches/ps646/products_tech_note09186a00800feff5.shtml

"Using Time Ranges with ACLs"

http://www.cisco.com/en/US/products/hw/switches/ps646/products_configuration_guide_chapter09186a00802cb80a.html#wp1035167

"Managing the System Time and Date" (for NTP)

http://www.cisco.com/en/US/products/hw/switches/ps646/products_configuration_guide_chapter09186a00802c9a36.html#wp1154144

Hope this helps! Please use the rating system.

Regards, Martin

[quintin]

Thanks I'll look these over

[quintin]

Do you need to have the Policer AND the ACL? Would the the ACL be enough on its own?

[mheusinger]

Hi,

the ACL will either completely block traffic or allow it. Depending on your requirements this might be the proper approach. But then you need to make sure all necessary traffic does not get blocked, like administrative access or the like.

A policer will allow traffic, but provide an upper speed limit.

Which option is favourable in your specific case depends on your policy regarding proper network use.

Hope this helps!

Regards, Martin

[quintin]

Essentially I don't want to block ANY traffic, just throttle it during work hours, then open it up during non-work hours.

[mheusinger]

Hi,

if you want to throttle it, then a policer (or shaper) will be required.

The ACL will just describe to the policer, which traffic to throttle, based on time of day. A sample config partially from the links above:

access-list 100 permit ip any any time-range ...

!specify the time range when traffic should be limited

class-map ip

match access-group 100

mls qos aggregate-policer all-traffic 8000 8000 exceed-action drop

policy-map police-IP-traffic

class ip

police aggregate all-traffic

interface gigabitEthernet 0/7

service-policy input police-IP-traffic

You can adjust the ACL to match only specific traffic and also adjust the rate limit in the policer to your requirements.

Hope this helps!

Regards, Martin

[quintin]

Thank you very much