LLDP Configuration

Unanswered Question

Hi There,

I am looking into the possibility of using LLDP on our Cisco switches for our Avaya IPT systems.

We use Cisco 3750 Standard POE swithces. I have looked at the following configuration guide on configuring LLDP.


According to this LLDP should be enabled globally but I can see no way of confirming this. I also do not have any of the LLDP commands available in global configuration mode.

Does anyone have any experience with LLDP.

I have this problem too.
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JanASvane Tue, 10/07/2008 - 09:07

We are running lldp on 3560 and 2960 switches and utilize it via a "lldp run" in Global Configuration" mode.

The problem that it gives us is that it forces a Network policy on all ports where it remarks dcsp and COS to "0" thereby making it impossible to trust the , In our case dscp setting from the Nortel phone.

But LLDP currently helps us putting the Nortel phones in the right voice VLAN.



Darren Ramsey Sun, 11/23/2008 - 21:05


Is there any update on this DSCP remarking issue with Nortel IP phones? I'm seeing the same issue even with the latest 3750 code 12.2(46)SE and the latest Nortel UNIStim3.1 firmware. Not sure if this is a Cisco issue or Nortel issue, but our Cisco 7965 works just fine, DSCP is marked and trusted.

I would have to say this is a Cisco issue. I am currently in the same boat using Cisco 3750 switches and Avaya phones. What I have noticed it that our call manager sets the DSCP setttings correctly and then after about 6 seconds after the phone comes up the QoS settings are then zeroed out. I was sure it was the phones as I didn't think that the DSCP setting would be set by LLDP since there is no way to configure that. But after grabbing a packet capture of the LLDP packets sent by the switch I saw under the Network Policy TLV that the switch is sending the following info: Policy, Tagged, Vlan ID, L2 Priority, and DSCP Value. Of which both are set to 0.

If I turn off this MED-TLV then the settings stay, however I need it for the VLAN ID like everyone else.

Does anyone know how to remove the QoS values from the the Network Policy TLV or if it is even possible.

I have tried this on IOS version 12.2(37) and 12.2(46) and both come out with the same outcomes.

Any suggestions? Any Cisco techs reading this?



Darren Ramsey Wed, 01/07/2009 - 16:20

Yes, this is a Cisco issue. The phones are requesting a DSCP 40 and the switch is overriding and sends back a DSCP 0 in the LLDP MED-TLV. This is scheduled to be fixed in 12.2(50)SE sometime in March. The 3750 will send a DSCP 46 back to the phone, but I don't know if that value will be user configurable.


Thanks dvr0 for the info!

OK, I am curious if this works for anybody else besides me. I was creating my own LLDP packets and tracking the packets from the switch. At that point I lowered the LLDP advertising timer to 15. Then noticed that all the DSCP settings were now staying and not being overwritten even though the LLDP packets still list it as zero. Can anyone else see if this happens to them. I do not know why it works. I will use this until Cisco releases a fix, but am curious if it may have been something else I did. If I put it to 30 it fails, back to 15 it works.



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