Cisco QoS + Link Speeds

[martynch1]

Hi all,

I’m wondering what the best practice is for setting WAN/Uplink speeds for links that are different speeds.

Look at the attached image, we have a 10Mbps Wan link to a site Router, then from the Router connected to a Switch with a 100MBps Uplink

I’m going to Auto QoS the Switch and trust Cisco Phone then build a QoS profile for the Router, but before I start to build QoS; would you fix the uplink speed of the Switch to the Router as 10Mbps and let Auto QoS deal with the shaping?

Thanks

Martyn

[Mark Malone · Accepted solution]

Hi
the WAN link will always be a choke point due to cost of the links , keep it simple , use auto qos on lan and uplink ports to the router, then you could use MQC QOS on the WAN circuit port shape police whatever you need , you can also shape the traffic coming from the LAN switch on the router inside LAN port too if required , we do this too , so an MQC QOS class-map/policy on router WAN and LAN port , the WAN would probably be sufficient , LAN QOS is not always required and actually in some cases can cause extra problems and issues , so be careful deploying it , check the queues when deployed , if MLS check the statistics and buckets , sometimes traffic can be dumped into 1 bucket constantly say out of 4 causing that buffer to fill and drop , that can be side effect of auto and mls qos , most of the time it works great though with little manual overhead required

[martynch1]

Many thanks for your response.

Martyn

[martynch1]

Would you match the uplink speed of the Switch with Router's WAN link?

[paul driver]

Hello 

I would say no need to -as Mark stated you could apply some moc qos to shape egress wan traffic on your wan rtr inline with changing the default queuing method from FIFO to WFQ this way not only will you be traffic shaping you would also be applying some fairness to all traffic exiting the wan rtr without any random drops.

[Mark Malone]

Yes agree with Paul there too, let the queuing and the qos do the work leave the speeds at default

[Joseph W. Doherty]

When it comes to QoS, "best practice" isn't well defined. "One size" seldom fits all.

Anytime you have more ingress bandwidth then egress bandwidth, you may have congestion.

Personally, I recommend using QoS at any point where congestion causes issues. Further, I recommend using QoS that meets your service requirements. (If auto-QoS does meet your requirement, sure, why not use it. Keep in mind though, it's possible for QoS, especially not configured for your requirements to make matters worse [this applies to auto-QoS too].)