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LLDP-MED and QoS DSCP Marking

 
ukonstantin
Occasional Advisor

LLDP-MED and QoS DSCP Marking

Hi all,

we are having a HP Switch 1920 with the following port configurations:

interface GigabitEthernet1/0/1
 port link-type hybrid
 port hybrid vlan 20 tagged
 port hybrid vlan 1 untagged
 undo voice vlan mode auto
 voice vlan 20 enable
 port auto-power-down
 poe enable
 stp edged-port enable
 lldp compliance admin-status cdp txrx
 lldp voice-vlan 20

 

 

I want to make sure that the DSCP of VOICE VLANs are not changed. And regarding the data vlan the dscp values shouldn't trust. 

Our customer tell me that the configuration above trust the DSCP values from the VOICE VLAN. As I understand it right normally w/o the command "dscp trust" all DSCP markings should be set to "0" zero...

I search for detailed informations but didn't find it...

Any help ?

 

Thanks

Udo

 

3 REPLIES
16again
Respected Contributor

Re: LLDP-MED and QoS DSCP Marking

Interfaces without  "qos trust  dscp|qos "  don't trust any incoming packets, all packets will end up in the switch low prio queue.
Also DSCP values aren't remarked/reset, since this requires  the "qos apply policy ...." interface command  (and a configured policy).

ukonstantin
Occasional Advisor

Re: LLDP-MED and QoS DSCP Marking

Please let me confirm..

All packtes whicht are coming from an IP Phone with DHCP EF and maybe a packet coming from a PC behind the Phone are not remarked?! 

The only reason for the command "qos trust dscp|cos" is to put the traffic in an explicit queue? 

Regarding Cisco this is different. Because without the command dscp trus all packets marked down to zero. 

So when I need to control the remarking I should configure a policy and apply it to the interface?! 

 

16again
Respected Contributor

Re: LLDP-MED and QoS DSCP Marking

"The only reason for the command "qos trust dscp|cos" is to put the traffic in an explicit queue? "
Yes
"So when I need to control the remarking I should configure a policy and apply it to the interface?! "

Yes,
Just as you would in Cisco land:  Default, Cisco also doesn't remark dscp value of packets.  You need to configure specific Cisco MPF commands to do this.