"mls qos trust dscp" not working on new cisco 2960 poe switch

DBCSNA
DBCSNA used Ask the Experts™
on
Hello,

We are in the process of upgrading our current Cisco Catalyst 3560 Series POE switch to a Cisco Catalyst 2960 Plus Series SI POE.

The config below is what we have in our current switches
 when we try to transfer the config to the new switch, we get an error on the line below:
 
mls qos trust cscp

it does not like cscp, its not recognized. if I change it to COS it does not take,

my question is why it does not take cscp and what the difference is between CSCP and COS. We run voice over ip phones on these switches. the phones and phone system are Siemens.

interface FastEthernet0/46
 switchport access vlan 501
 switchport mode access
 switchport voice vlan 101
 speed 100
 duplex full
 priority-queue out
 mls qos trust dscp
 spanning-tree portfast
mlscos.jpg
Comment
Watch Question

Do more with

Expert Office
EXPERT OFFICE® is a registered trademark of EXPERTS EXCHANGE®
kevinhsiehNetwork Engineer

Commented:
If I am not mistaken, the 3650 is a L3 switch and the 2960 is L2. DSCP is L3 QoS which isn't understood by L2 switch, which only understands COS.

You probably only need priority queuing on interfaces where there is a difference in bandwidth and there is contention,  like on your WAN interface. I have IP phones on over a dozen different 2960 switches and have no issues without using COS. I do have QoS on the WAN interfaces of my routers, but nothing for the LAN.
Distinguished Expert 2018
Commented:
There are actually commands to map COS to DSCP (and vice versa) on Catalyst switches, but I guess the easiest way to configure QoS would be to use auto qos (the same article as above).

(config)# mls qos
(config)# interface Fa0/46
(config-if)#  auto qos voip {cisco-phone | cisco-softphone | trust}

When you enter the auto qos voip trust interface configuration command on a port connected to the network interior, the switch trusts the CoS value for nonrouted ports or the DSCP value for routed ports in ingress packets (the assumption is that traffic has already been classified by other edge devices).
The Switch in that case will do automatically for you next configuration changes (quote from CCNP switch 642-813 official certification book)
- Enabling QoS
- CoS-to-DSCP mapping for QoS marking
- Ingress and egress queue tuning
- Strict priority queues for egress voice traffic
- Establishing an interface QoS trust boundary

Author

Commented:
Thank you KevinHSieh and Predrag Jovic, for helping clarify some of the confusion that i had.

Indeed the catalyst 3650 switches are layer 3 and the new switches 2960 are layer 2.

Do more with

Expert Office
Submit tech questions to Ask the Experts™ at any time to receive solutions, advice, and new ideas from leading industry professionals.

Start 7-Day Free Trial