3Com Switch with CCM -- DHCP Option 184

Unanswered Question
May 2nd, 2007
User Badges:

I am in the situation of making Cisco CallManager 4.1(3) and 7961 phones work on a 3Com 7757 switch. The network is designed with a Cisco 6509 as the Core switch, and four 7757s connected to it for users. I am able to get the phones to work on the 3Com, but I can't get DHCP option 184 working properly on my MS Windows 2003 DHCP Server. As a result, the phone never gets tagged to the voice VLAN and never gets the IP address from the scope I have identified for voice, it only gets an address from the scope for the data network. Anyone out there have any experience in this area? Yes, I know it would have been easier to stay all Cisco, but this was done before I got here. Thanks in advance.

  • 1
  • 2
  • 3
  • 4
  • 5
Overall Rating: 4.5 (2 ratings)
Rajesh Revuru Wed, 05/02/2007 - 07:02
User Badges:
  • Silver, 250 points or more

Hey Joe:

We are using Windows 2003, and cisco 3560. But we are using DHCP option 150.

Also i am not sure about 3com switches.

I had to include ip-helper-address of dhcp server on cisco switches.

Let me know

joe.ainsworth Wed, 05/02/2007 - 07:07
User Badges:

The problem is the phones are to be connected to the 3Com, and they support Option 184, not 150. The phones can access the DHCP server, but because there is not an Option 184 on the network right now, the phones do not tag to the voice vlan. So the big question is, how can I create option 184 for use with Cisco phones on 3Com switches for VoIP, on the Windows 2003 DHCP?


Tim Smith Wed, 05/02/2007 - 07:12
User Badges:
  • Silver, 250 points or more

Hi Joe,

Are you trying to use DHCP option 184 to tell Cisco phones what their voice VLAN is?

Cisco IP phones would get their voice VLAN from CDP usually.

Only other option is to hard code it on the phone.

Or use a seperate switch port just with the phone - obviously not very workable.

Actually just found a 3com doc.. that explains it.


Option 184 wont work with Cisco, but there is another Cisco compatibility feature on the switch. Check out page 9 of that doc!

Hope that helps!



joe.ainsworth Wed, 05/02/2007 - 07:25
User Badges:

Thanks Tim, I actually was working from the very same PDF. Unfortunately, the command is not available. In reviewing the doc again, I noticed that it requires software version 3.02.02 or higher in this example (for the 5500). I checked my switch and it has version 3.02.00r. I am going to check 3Com and see if there is an upgrade.

Tim Smith Wed, 05/02/2007 - 07:39
User Badges:
  • Silver, 250 points or more

Hi Joe,

Ah ok no probs.. I did notice that. What a shame they stuck the 3coms in really. But still, very decent of 3com to add those features, and quite well documented i thought!

Pretty sure that spoofing the CDP with the 3com is your only hope.. Cisco phones wont boot with the 184 option.

Let us know if they come back with a supported option in that platform.




This Discussion