Qos : dscp removed on router port

[jmolines42]

Hello,

I have a problem with dscp preservation on a WS-C3750X-48 catalyst; in my little diagram, his name will be SW2, so I have this:

SW1 <-> SW2 <->RT1

some phone connected to SW1 mark with dscp EF (46) the voice traffic

The "mls qos" was enabled on SW1 and SW2

The interlink switch ports has the "mls qos trust dscp" option, the phone port and the router port also.

And the problem is I can see the dscp marking on the SW2 when I span the voice vlan on this switch but the dscp was removed ( DSCP set to 0) on the router port ( span on the router port for look )

If I made also a packet capture on the router RT1, I see the DSCP was effectively reset to zero

If I disable the "mls qos" on SW2, of course all is fine and the dscp was preserved and forwarded to the router

thanks for any tips

SW1:

sw-par1-14-02-new#sh ver
Cisco IOS Software, C3750E Software (C3750E-UNIVERSALK9-M), Version 12.2(55)SE3, RELEASE SOFTWARE (fc1)
Technical Support: http://www.cisco.com/techsupport
Copyright (c) 1986-2011 by Cisco Systems, Inc.
Compiled Thu 05-May-11 15:40 by prod_rel_team
Image text-base: 0x00003000, data-base: 0x02800000

ROM: Bootstrap program is C3750E boot loader
BOOTLDR: C3750E Boot Loader (C3750X-HBOOT-M) Version 12.2(53r)SE2, RELEASE SOFTWARE (fc1)

sw-par1-14-02-new uptime is 19 weeks, 2 days, 19 hours, 56 minutes
System returned to ROM by power-on
System restarted at 20:59:31 CET Fri Jan 11 2013
System image file is "flash:/c3750e-universalk9-mz.122-55.SE3/c3750e-universalk9-mz.122-55.SE3.bin"

This product contains cryptographic features and is subject to United
States and local country laws governing import, export, transfer and
use. Delivery of Cisco cryptographic products does not imply
third-party authority to import, export, distribute or use encryption.
Importers, exporters, distributors and users are responsible for
compliance with U.S. and local country laws. By using this product you
agree to comply with applicable laws and regulations. If you are unable
to comply with U.S. and local laws, return this product immediately.

A summary of U.S. laws governing Cisco cryptographic products may be found at:
http://www.cisco.com/wwl/export/crypto/tool/stqrg.html

If you require further assistance please contact us by sending email to
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License Level: lanbase
License Type: Permanent
Next reload license Level: lanbase

cisco WS-C3750X-48 (PowerPC405) processor (revision B0) with 262144K bytes of memory.
Processor board ID FDO1541R1HJ
Last reset from power-on
2 Virtual Ethernet interfaces
1 FastEthernet interface
104 Gigabit Ethernet interfaces
4 Ten Gigabit Ethernet interfaces
The password-recovery mechanism is enabled.

512K bytes of flash-simulated non-volatile configuration memory.
Base ethernet MAC Address       : 64:9E:F3:11:03:80
Motherboard assembly number     : 73-12552-05
Motherboard serial number       : FDO15421422
Model revision number           : B0
Motherboard revision number     : C0
Model number                    : WS-C3750X-48T-L
Daughterboard assembly number   : 800-32727-01
Daughterboard serial number     : FDO15420MSC
System serial number            : FDO1541R1HJ
Top Assembly Part Number        : 800-31326-02
Top Assembly Revision Number    : E0
Version ID                      : V02
CLEI Code Number                : COMJT00ARB
Hardware Board Revision Number  : 0x03

Switch Ports Model              SW Version            SW Image                
------ ----- -----              ----------            ----------              
     1 54    WS-C3750X-48       12.2(55)SE3           C3750E-UNIVERSALK9-M    
*    2 54    WS-C3750X-48       12.2(55)SE3           C3750E-UNIVERSALK9-M    

Switch 01
---------
Switch Uptime                   : 19 weeks, 2 days, 19 hours, 45 minutes
Base ethernet MAC Address       : 64:9E:F3:14:B6:00
Motherboard assembly number     : 73-12552-05
Motherboard serial number       : FDO154213QX
Model revision number           : B0
Motherboard revision number     : C0
Model number                    : WS-C3750X-48T-L
Daughterboard assembly number   : 800-32727-01
Daughterboard serial number     : FDO15420N7S
System serial number            : FDO1541R1HH
Top assembly part number        : 800-31326-02
Top assembly revision number    : E0
Version ID                      : V02
CLEI Code Number                : COMJT00ARB
License Level                   : lanbase
License Type                    : Permanent
Next reboot licensing Level     : lanbase

Configuration register is 0xF

sw-par1-14-02-new#sh license
Index 1 Feature: ipservices    
        Period left: 8  weeks 4  days
        License Type: Evaluation
        License State: Active, Not in Use, EULA not accepted
        License Priority: None
        License Count: Non-Counted

Index 2 Feature: ipbase        
        Period left: 0  minute  0  second 
Index 3 Feature: lanbase       
        Period left: Life time
        License Type: Permanent
        License State: Active, In Use
        License Priority: Medium
        License Count: Non-Counted

Abdessamad

[paul driver]

Hello
You don't say you have auto qos enabled or not

By default cos 5/dscp 40 is the setting on these switches on the voip phones i think this is set to default dscp to 46 but this is automatically change on the switch when auto qos is applied to the port to be cos5/dscp46

if auto qos isnt enabled you have to manually change it on the switch as a global setting to read dscp 46

Sh mls qos maps cos-dscp
Mls qos maps cos-dscp 0 8 16 24 32 46 48 56


Also
On switch 2 trust dscp on the trunk between the two switches or disable the dscp rewrite on switch 2
No mls qos dscp rewrite but still do the cos-dscp map change.
Res
Paul

Sent from Cisco Technical Support iPad App

[jmolines42]

thanks for your reply

no auto qos, only mls qos enabled

The trunk between the switch was already trusted

SW1 and SW2 has the same config,

SW1#sh mls qos

QoS is enabled

QoS ip packet dscp rewrite is enabled

SW2#sh mls qos

QoS is enabled

QoS ip packet dscp rewrite is enabled

when the packet was send to the router port, DSCP rewrited to zero or removed

Abdessamad