Problem setting up Cisco 68xx series IP Phone using LLDP.

[euforiamracademia]

Hi,

I have just recently bought (thanks to recommendation from @ vishalbhandari) Cisco 6841 for my project. It is a test unit. I want to configure it so that it receives Network policy (vlan, pcp, dscp) via LLDP-MED. The switch to which it is connected, is 3-rd party linux switch, which I have configured to bridge between several different ports. Each of the port members accept vlan 100 and vlan 200. The bridge also has PVID 1 set for untagged frames, and all the member ports understand pvid=1. For LLDP, I am using lldpd, which I have configured to send LLD-MED Network Policy TLVs (Vlan 100, PCP: 5, DSCP:36). I have captured traffic to make sure the TLV gets attached to LLDP broadcasts, and it does. My problem is that the phone doesn't seem to 'accept' that configuration. Is there anything specific I need to do or ensure before the phone accepts received config ? How do I tell the phone to use other vlan (e.g. vlan200) for data traffic (i.e. one coming from PC port) ?

In order to achieve voice-only policy that I am broadcasting, I have tried:

- Fresh out of the box phone,

- Set IPv4 address manually,

- Set it to IPv4 only,

- Disabled CDP,

- Vlan Tagging off,

I was expecting, that the phone would receive config, and set itself up, accordingly, i.e. start using vlan tagging, with vlan100 for voice. But this doesn't seem to work, i.e. the phone seems to still be using untagged frames. Is directly turning off vlan tagging (with LLDP enabled) still 'stronger' than the config received via LLDP ? Any help would be greatly appreciated.

BTW. How do I make direct IP calls from 6841 (i.e. without PBX,etc.) ?

[Maren Mahoney]

The answer will depend in part on whether you purchased Enterprise or MPP version phones (CUCM-based or 3rd-party PBX respectively). I am providing a link to the 8800 series MPP guide that describes the interaction of LLDP with the phones. The firmware for the 9800 series should be the same for LLDP. Note that there are required TLVs in the LLDPDU that, if not included, will cause the phone to ignore the messages:

Cisco IP Phone 8800 Series Multiplatform Phone Administration Guide - LLDP-MED 

I hope this is helpful. Let us know if it is not or if you have more questions.

Maren

[euforiamracademia]

Hi Maren,

Thank you for trying to help me out. I have a MPP version of the phone. I have seen the documentation piece that you have linked. Interestingly, when you read through it, it seems that most TLVs are simply ignored and not validated in case of incoming LLDP frames. The one that seems to be validated is LLDP-MED Network policy. The LLDP frames sent by the switch seem to conform to what have been described in linked documentation. I've also disabled CDP, to make sure it does not interfere in any way.

One more thing that I have noticed (see the screenshot) is that albeit CDP being off, the phone still sends CDP(?) frames, but LLDP agent on the switch sends LLDP frames. I find this curious.

[Nithin Eluvathingal]

68XX phones are MPP and no  need to be converted to MPP. It’s still not clear what your problem is. Are the phones not getting an IP address, or are they not registering with the third-party PBX?

If the issue is that the phones are not registering with the PBX, have you accessed the web GUI of the phone and configured the proxy server IP address, extensions, user ID, and password for the phone to register?

Regarding your question about making calls without any PBX, it’s not possible to use the phones as standalone devices. The phones must register with some call control platform to make calls. If you don’t register the phone to a call control platform, how do you expect to have a dial tone and dial numbers?

You can register the device to a PBX on your premises or subscribe to a service from a cloud provider and register with them. In any case, the phone must register with some call control platform to make calls.

[euforiamracademia]

Nitin, please read my post again. The phone is not using LLDP network policy (VLAN information, pcp, dscp) that is being advertised by the switch. It has nothing to do with PBX. I am asking about using the phone without PBX, because many (in fact most of) non-Cisco phones allow for direct IP call without PBX. You just type in IP address of your peer, et voilla ! I thought that CISCO phone would also be able to do just that, but it doesn't seem so.

[Maren Mahoney]

The part I was focusing on in the doc I linked to was:

The outgoing LLDPDU contains all the preceding TLVs if applicable. For the incoming LLDPDU, the LLDPDU is discarded if any of the following TLVs are missing. All other TLVs are not validated and ignored.

• Chassis ID TLV
• Port ID TLV
• Time to live TLV
• LLDP-MED Capabilities TLV
• LLDP-MED Network Policy TLV (for application type=Voice only)
• End of LLDPDU TLV

When you wrote "The LLDP frames sent by the switch seem to conform...." do you mean that all of the above are included? 

The phone sending CDP by default is normal, as the product is Cisco. (Of course....lol) When I have worked with LLDP it has been in an enterprise environment where LLDP was enabled on the phones as part of their registration process to CUCM, with the two coexisting until LLDP is fully set up. So I don't have experience doing what you are trying to do.

From what I know of the 6800 series phones, they are (I thought) supposed to send/respond to both CDP and LLDP out of the box. So I'm hoping the other smart folks on the thread can help because I'm at about the edge of what I know about LLDP.

Maren

[euforiamracademia]

Yes, that's exactly what I meant. All these required TLVs are sent, even order matches that required.

[euforiamracademia]

Hmm after disabling dot3 tlvs the phone now at least applies DSCP values advertised by LLDP-MED network policy TLV, that's almost a success..Right now what's missing is to apply advertised VLANid for voice traffic.

[euforiamracademia]

Please correct me if I understand it wrong, but (quote from the link posted by @Maren Mahoney

---

QoS Resolution for LLDP-MED

If CoS is applicable and if CoS = 0, the default is used for the specific extension as previously described. But the value shown on L2 Priority for TLV for outgoing LLDPDU is based on the value used for extension 1. If CoS is applicable and if CoS != 0, CoS is used for all extensions.

If DSCP (mapped to ToS) is applicable and if DSCP = 0, the default is used for the specific extension as previously described. But the value show on DSCP for TLV for outgoing LLDPDU is based on value used for the extension 1. If DSCP is applicable and if DSCP != 0, DSCP is used for all extensions.

If the VLAN > 1 and VLAN < 4095, the VLAN is set accordingly. CoS and ToS are based on the default as previously described. DSCP is applicable.

If there is a valid network policy for the voice application from LLDP-MED PDU and if the tagged flag is set, the VLAN, L2 Priority (CoS), and DSCP (mapped to ToS) are all applicable.

If there is a valid network policy for the voice application from LLDP-MED PDU and if the tagged flag is not set, only the DSCP (mapped to ToS) is applicable.

The Cisco IP Phone reboots and restarts the fast start sequence.

 In theory, if received LLDP-MED Network Policy frame has a policy with valid DSC, VLAN, PCP values, and TAGGED bit is set, such configuration should be applied by the phone. In practice it is not. It seems like it is working as follows:

- If DSCP value in received policy is the same as current phone settings then do nothing. Ignore other values (even if priority has changed)

- If DSCP value in received policy is not the same as current phone settings, then apply everything *except* for vlan.

I am attaching packet capture screenshot with logging info sent to syslog server, that for some reason vlanId is set to 0.

[euforiamracademia]

OK, after extensive testing, I have to conclude that 6841 is incapable of utilizing VLANID information from LLDP-MED Network Policy TLV. It can apply dscp and priority, but ignores vlan information. Better than nothing I guess.

[Maren Mahoney]

I'm sorry you were unable to make it work. If you have a service contract you could contact TAC for assistance, but I'm guess you would have thought of that already if you did. 

Maren

[euforiamracademia]

Hi Maren. I don't have a service agreement, and I only have one unit. I bought this unit for testing VoIP feature that is just a small feature for much larger R&D project I am conducting, and that is focused on something else entirely. Hence no service agreement Thank you for your help.

[euforiamracademia]

Hello there. Any chance someone has any working IP phone that is correctly configuring itself according to what was sent via LLDP-MED Network Policy and could provide me with a pcap file (packet dump) for that exchange ?