QoS
QoS is covered in detail in Chapter 31, and itâs a topic that could easily fill an entire book. In this section, I will focus on some 3750-specific QoS features.
One of the useful features of the 3750 is support for AutoQoS, which makes certain assumptions about your network and configures the switch accordingly. While Iâm not a fan of letting network devices assume anything, in this case, the assumptions are accurate most of the time. I have had no qualms about enabling AutoQoS on the 3750s Iâve installed in VoIP networks with hundreds of phones supported by Cisco Call Manager. The reason Iâm OK with this is that Ciscoâs assumptions are built around the idea that youâre using Call Manager, Cisco IP phones, and low-latency queuing on your network. Chances are, if you need QoS enabled on your switches, itâs because youâre implementing VoIP.
You can enable AutoQoS on an interface with the auto qos voip
command:
3750(config-if)#auto qos voip ?
cisco-phone Trust the QoS marking of Cisco IP Phone
cisco-softphone Trust the QoS marking of Cisco IP SoftPhone
trust Trust the DSCP/CoS marking
There are three options: cisco-phone
, cisco-softphone
, and trust
. The first two are used for interfaces
connected to either hard- or softphones. When configured with these
options, the QoS values received in packets will be trusted only if
theyâre sourced from Cisco IP phones. The trust
option enables QoS while trusting all
packetsâ QoS values.
If youâd like to see what AutoQoS ...
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