09-20-2011 06:11 AM - edited 03-04-2019 01:39 PM
Hello all -
I have a 50 Mbps metro ethernet connection between our main office, and our collocation site, where we store web servers, DR equipment and VPN access gateways. I have two Cisco 3845 ISR's connected to the metro E circuit. The interfaces on each router are configured as 100/full as requested by my ISP. We are connected via ethernet to a fiber media converter.
As I understand, CBFWQ will not kick in until congestion occurs on an interface. I also understand that the bandwidth command on an interface is to provide bandwidth related information to upper level protocols (like EIGRP, etc).
My question is that since the interface where I have CBWFQ configured on is at 100 Mbps, but my circuit is at 50Mbps, how can I get my routers to kick CBWFQ in when traffic demand exceeds 50Mbps+? Does the bandwidth command on the interface control that as well?
Thanks for any suggestions.
Brantley
Solved! Go to Solution.
09-20-2011 07:05 AM
You need to do HQoS. Here is a sample config:
policy-map PARENT
class class-default
shape average 50000000
service-policy CHILD
policy-map CHILD
class CLASS1
class CLASS2
... SNIP...
HTH,
jerry
09-20-2011 07:07 AM
Brantley
So you want to apply CBWFQ to the 50Mbps of traffic ? If so then you need to use hierarchical QOS ie. you first apply a shaper to the interface to shape the traffic to 50Mbps. Then within that shaped traffic you can apply child policies which apply CBWFQ to the shaped traffic. See this link for configuration details -
http://www.cisco.com/en/US/customer/docs/ios/qos/configuration/guide/qos_frhqf_support.html
Jon
09-20-2011 07:05 AM
You need to do HQoS. Here is a sample config:
policy-map PARENT
class class-default
shape average 50000000
service-policy CHILD
policy-map CHILD
class CLASS1
class CLASS2
... SNIP...
HTH,
jerry
09-20-2011 07:07 AM
Brantley
So you want to apply CBWFQ to the 50Mbps of traffic ? If so then you need to use hierarchical QOS ie. you first apply a shaper to the interface to shape the traffic to 50Mbps. Then within that shaped traffic you can apply child policies which apply CBWFQ to the shaped traffic. See this link for configuration details -
http://www.cisco.com/en/US/customer/docs/ios/qos/configuration/guide/qos_frhqf_support.html
Jon
09-20-2011 07:34 AM
Thanks guys! This was just want I was looking for!
09-20-2011 10:01 AM
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The Author of this posting offers the information contained within this posting without consideration and with the reader's understanding that there's no implied or expressed suitability or fitness for any purpose. Information provided is for informational purposes only and should not be construed as rendering professional advice of any kind. Usage of this posting's information is solely at reader's own risk.
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Posting
One possible "gotcha", if your provider is providing you 50 Mbps, this often means you get 50 Mbps of wire bandwidth. Unfortunately, I don't believe all IOS shapers account for L2 overhead. When they don't, if you need to increase the accuracy of your shaping, you need to reduce the shaper's CIR to allow for L2. Also unfortunately, L2 overhead varies by packet/frame size, so for super accuracy you need to allow for worst case.
For run-of-the-mill traffic shaping, and assuming you're not running, sustained, 100% logical link capacity, setting the shaper to nominal CIR is fine.
09-21-2011 06:03 AM
I did not think of L2 overhead, but are not running at 100% all of the time. In fact we run around 60-70% (replication).
I don't think right now it has to be spot on, since our ISP does allow bursting and some overages. I just wanted some type of QoS in place to make sure we did not exceed 50 often so that we are not charged extra.
Thanks to all for contributing!
09-21-2011 09:44 AM
Disclaimer
The Author of this posting offers the information contained within this posting without consideration and with the reader's understanding that there's no implied or expressed suitability or fitness for any purpose. Information provided is for informational purposes only and should not be construed as rendering professional advice of any kind. Usage of this posting's information is solely at reader's own risk.
Liability Disclaimer
In no event shall Author be liable for any damages whatsoever (including, without limitation, damages for loss of use, data or profit) arising out of the use or inability to use the posting's information even if Author has been advised of the possibility of such damage.
Posting
Then you'll likely be fine, as that sounds "run-of-the-mill".
If you were also dealing with VoIP traffic, then often you do need to be more "spot on".
Oh, and although you note you only "In fact we run around 60-70% (replication).", such can be deceptive since generally average usage is often measured across minutes. Again, for your purpose to avoid extra bandwidth charges, this shouldn't be an issue.
PS:
If your provider allows bursting, and if they don't charge for it when you use it, you might also use shape peak vs. shape average.
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