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4500 and 5500 switches Voice Vlan problems

 
Rob_Korn
Advisor

4500 and 5500 switches Voice Vlan problems

I am having trouble making the Polycom phones use the Voice Vlan feature of the 4500 and 5500 switches.





I have created all of the configuration but the phones do not AUTOMATICALLY enter the Voice vlan.





If I set the Vlan on the phone itself, no problem.  If I have my DHCP send the vlan info to the phone on boot up, no problem.





I was/am under the impression that one of the functions of the "Voice Vlan 98 enable" and "Voice vlan mode auto" commands was to get the switch to check the MAC address against the OUI list and if a match, move the device to the proper vlan automatically.





 





I have been told that this is "unsupported", yet I read throughout the manuals and configuration examples that I am correct.





Anyone have any input or suggestions?





 





Thanks.





Rob Korn.



7 REPLIES
Fred_Mancen_1
Super Advisor

Re: 4500 and 5500 switches Voice Vlan problems

Did you already checked the DHCP Option in the DHCP Scope properties? The Avaya IP phones use the 176 and 246 options; the Polycom phones may use an option that is not properly set in the DHCP scope properties.



A few months ago we faced a similar issue in a customer project, when the IP phones were getting a VLAN ID different from the voice VLAN that we had set in the switches (5500 and 4500, also) and our system engineer figured out that the problem was this.



HTH



Rob_Korn
Advisor

Re: 4500 and 5500 switches Voice Vlan problems

 I have the phones working properly IF I send the vlan id out in the DHCP.



That is not the issue....  The issue is that this should not be necessary as per the documentation and sales information.  3Com specifically states in the "Advance Config Guide":



 





"In automatic mode, the switch configured with voice VLAN checks the source 



MAC address of each incoming packet against the voice device vendor OUI. If a 



match is found, the switch assigns the receiving port to the voice VLAN and tags 



the packet with the voice VLAN ID automatically."



 



Therefore, Vlan ID in the DHCP should not be needed.



 



 





Fred_Mancen_1
Super Advisor

Re: 4500 and 5500 switches Voice Vlan problems

As far as I know the voice VLAN feature helps to ensure a best priority to the voice traffic. This solution you are mentioning is not possible since the switch does not have a IP pool to act as a DHCP server, because if the phone obtains a VLAN ID, it will need an IP address also, right? How the switch could configure a port itself with a VLAN ID and the DHCP server would provide an IP address? I'm not sure if I understand your doubt and needings...sorry.



 



Rob_Korn
Advisor

Re: 4500 and 5500 switches Voice Vlan problems

 You are not understanding.  



According to the passage I quoted, and the information given to me pre-sales, the switch will handle the insertion into voice vlan based upon Mac address OUI match.  



There is nothing confusing about the item I quoted, it states that the phone will be placed into the proper vlan based on the OUI match.  



At that point, once the phone is on the vlan, then the DHCP on that vlan should take over.



Thanks for responding.



I understand the auto QOS features, and that is nice (if it were documented).  But that doesn't explain why 3Com themselves do not seem to know what this software is supposed to do.  Very frustrated user here.



Rob.



 



Rob_Korn
Advisor

Re: 4500 and 5500 switches Voice Vlan problems

 Found the trick.



The issue is the command " Voice vlan legacy".  Don't really know what this does but as soon as I issued it the phones were placed in the correct vlan AUTOMATICALLY - no DHCP options, NO setup of a voice vlan setting on the phone itself.



 



Here is a sample from config:



 





vlan 98



 name voice



#





interface Ethernet1/0/1



 poe enable



 stp edged-port enable



 port link-type hybrid



 port hybrid vlan 98 tagged



 port hybrid vlan 1 untagged



 undo jumboframe enable



 undo voice vlan mode auto



 voice vlan enable



 voice vlan legacy



 


 


Please note that I cannot find what the "legacy" parameter does, if anyone knows please speak up!


 


Thanks.  Rob.


 






Fred_Mancen_1
Super Advisor

Re: 4500 and 5500 switches Voice Vlan problems

It sounds good, Rob. Thanks for your feedback. I didn't know this command also.



Regards



vangass
Frequent Advisor

Re: 4500 and 5500 switches Voice Vlan problems

Hi,



According to the 5500 manual:


"  The voice VLAN legacy feature realizes the communication between 3Com’s device and other vendor’s voice device by automatically adding the voice VLAN tag to the voice data coming from other vendors’ voice device. The voice vlan legacy command can be executed before voice VLAN is enabled globally and on a port, but it takes effect only after voice VLAN is enabled globally and on the port.


"



Regards,


V.