DHCP for PC and IP Phone - Best Practices

Unanswered Question
Jul 12th, 2007


Are there any best practices for DHCP for your devices on a data or voice VLAN.


If I have data vlan of say, /24 and I have a voice vlan of /24

would it not be nice for troublshooting and design purposes to have the host portion as the same number?

ie, a PC would be and the phone would be

Just a thought?

Dont think it can be done?

If anyone has any ideas on this, please could you be so kind to let me know.

Many thx


I have this problem too.
0 votes
  • 1
  • 2
  • 3
  • 4
  • 5
Overall Rating: 0 (0 ratings)
johnhsnow Thu, 07/12/2007 - 06:18

HI Peter. It depends on the scope of your network but just to give you an example a contiguous block of Class B for voice and data might be something like this:

Data > /24 - You can further subnet this into /24's based on need and size of network ie..


Voice > /24


You cannot assign host addresses if you are using DHCP but you have control over the scopes.

Hope this helps.


kfarrington Thu, 07/12/2007 - 06:28

Thx for the speedy response John.

I just thought it would be nice if you could do something with the host portion.

Lets say that an IP Phone gets an address of, then the DHCP server when assigning the IP address of the PC plugged into the back of the phone, could somehow inspect the IP address of the phone, and try and assign the last octet as the same for the PC as the phone.

Hairbrained I know, but would be a good little feature?

Just a thought? and many thx for the reply :)

Kind regards,


kfarrington Thu, 07/12/2007 - 06:31

Also, the two DHCP scopes would have to be in sync, ie, if a phone had the address .1 but the PC was not turned on, the DHCP server would know that the .1 is assigned to a phone, and would not allocate the data DHCP address.

I dont know how this would fully work, as I say, a hairbrained idea I suppose



This Discussion