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Community Member

mls qos trust dscp??? is setting my DSCP values to zero!?

Hi,

I was just doing some testing to ensure that the command 'mls qos trust dscp' is working on my 6509 switches before rolling out QoS.

Before adding any configuration I could see using wireshark that traffic from my Avaya 9608 handset was coming through with a DSCP value of 46 (as it is supposed to).

I then added the command 'mls qos' (at global level)

on examining the wireshark output this time, the DSCP value had been set to zero (i.e. it defaulted it to best effort)

I then expected by adding the commmand 'mls qos trust dscp' on the interface the phone is connected to that the DSCP value would would again be left alone?

does anybody know why this is happening?

Many thanks in advance.

Andy

8 REPLIES
Community Member

mls qos trust dscp??? is setting my DSCP values to zero!?

no responses  

please let me know if I haven't made the question clear!!

Thanks...

Andy

VIP Purple

mls qos trust dscp??? is setting my DSCP values to zero!?

please show your complete qos-config and also the config of the port where your phone is connected.

-- 
Don't stop after you've improved your network! Improve the world by lending money to the working poor:
http://www.kiva.org/invitedby/karsteni

Community Member

mls qos trust dscp??? is setting my DSCP values to zero!?

Hi,

thanks for your reply.

mls qos

interface GigabitEthernet3/34

description *** DATA VLAN 35 - VOICE VLAN 34 ***

switchport

switchport trunk native vlan 36

switchport trunk allowed vlan 34,36

switchport mode trunk

mls qos trust dscp

no cdp enable

spanning-tree portfast trunk

If i don't include the global 'mls qos' command then the voice packets keep the dscp 46 value.  If I add the mls qos command this causes the switch to set the dscp values to zero.

???

Thanks again 

ps.  there are some other mls commands on the switch... i don't know if these could interfere but they were already on there so i'm reluctant to remove them..

Hall of Fame Super Blue

mls qos trust dscp??? is setting my DSCP values to zero!?

ps.  there are some other mls commands on the switch... i don't know if these could interfere but they were already on there so i'm reluctant to remove them..

Any chance you could post them ?

Jon

VIP Purple

Re: mls qos trust dscp??? is setting my DSCP values to zero!?

well, the other commands also control how QoS is handled by the switch ...

And in addition to that, post the output of "sh mls qos interface gig 3/34" while "mls qos" is enabled.

-- 
Don't stop after you've improved your network! Improve the world by lending money to the working poor:
http://www.kiva.org/invitedby/karsteni

Community Member

mls qos trust dscp??? is setting my DSCP values to zero!?

ah!

Sorry.. I meant to add the additonal commands that are present on the switch..

here they are!

mls ip slb purge global

mls netflow interface

no mls flow ip

mls cef error action reset

Community Member

mls qos trust dscp??? is setting my DSCP values to zero!?

Hi.

i tried the command -

sh mls qos interface gig 3/34

The switch wouldn't accept the interface part of the command?

RS03-6509E-DIST-ML-01#show mls qos ? 

  aggregate-policer  aggregate-policer keyword

  arp                arp keyword

  ip                 ip keyword

  ipv6               ipv6 keyword

  last               last keyword

  mac                mac keyword

  maps               maps keyword

  module             show entries in module

  protocol           protocol passthrough information

  statistics-export  QOS Statistics export

  |                  Output modifiers

 

thanks

Community Member

mls qos trust dscp??? is setting my DSCP values to zero!?

unfortunately I can't continue now as the security guard is kicking me out of the office now...  I'll be back tomorrow. 

thanks to everyone for their help this evening.

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