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Oct 15th, 2008

What are the detailed steps to deploy DHCP for IP phones on a router?

I have this problem too.
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Overall Rating: 4.8 (4 ratings)
Jaime Valencia Wed, 10/15/2008 - 05:24

there is plenty of documentation on if you are a little proactive and search before you ask

i just looked DHCP on CCO and got this:

Configuring DHCP

Cisco IOS DHCP Server

only particular need is to add option 150 (TFTP)



if this helps, please rate

singh-ashok Wed, 10/15/2008 - 22:20


Thanks for your help.

I have not worked much on routers / switches & all my experience is on Microsoft platforms. I am a baby on Cisco technologies.

Hence all these basic questions.

Have a nice day.

Thanks & Regards,


Md. Mijanur Rahman Wed, 10/15/2008 - 06:22

At the router where you will deploy DHCP server:


ip dhcp pool voice-xxx

network x.x.x.x 255.255.x.x

default-router x.x.x.x

option 150 ip a.a.a.a



ip dhcp pool data-yyy

network y.y.y.y 255.255.y.y

default-router y.y.y.y

dns-server b.b.b.b


option 150 ip would be the TFTP server IP (your publisher hopefully). And the default-router ip would be the Vlan interface IP.

At the access switch:


interface FastEthernet1/0/3

switchport access vlan xxx

switchport voice vlan yyy

mls qos trust device cisco-phone

spanning-tree portfast


Hope this help.

Please rate if helpful.

singh-ashok Thu, 10/16/2008 - 01:42

Thanks Rahman,

Is a scenario where the data scope is on the Domain Controller & Voice DHCP scope on the router feasible? Is there any special config required on the switch? I mean do we require to configure vlan trunking?



Md. Mijanur Rahman Thu, 10/16/2008 - 03:28

Hi, you will need some modification in configuration. If you want so,

first, remove the DHCP pool from you router,

second, configure a vlan for data at switch,

third, keep your windows DHCP server IP at that data vlan.

But I'm not sure how you will populate the TFTP server IP from windows DHCP server (like 'option 150 x.x.x.x' populate the TFTP server IP from router), hope you better know this.

singh-ashok Thu, 10/16/2008 - 04:19


There is no DHCP pool configured on the router right now, all PC's get their IP's from a Windows server & all phones use static IP's. We just want to change this ( the phone part) to DHCP.

My question is - when there is already a DHCP server for data on the Windows server, is it necessay to configure anything extra on the router? I mean some vlan or trunking?



Md. Mijanur Rahman Thu, 10/16/2008 - 05:25

>>when there is already a DHCP server for data on the Windows server, is it necessay to configure anything extra on the router?

:::::Yes you will need. Did you configure any data vlan for users? In not, create a vlan for data. Keep your DHCP server in that vlan.


At DHCP Server

IP Address pool:

Default Gateway at broadcast mode:

TFTP IP at broadcast mode:

At Router


interface Vlan

description **** DATA VLAN ****

ip address


Also you should create a voice DHCP pool in the router, set static IP in the phone is not a standard practice.

HTH, post if you need more.

singh-ashok Thu, 10/16/2008 - 05:58

This is a bit weird here , I will explain the scenario - there was a DHCP scope for Voice created on the CCM before but someone has deleted it by accident it seems. On the access switches, I see a vlan for voice ( but no vlan for data ). What I am trying to implement is to re-create the DHCP scope for IP phones on the router instead of the CCM.

There is no vlan for data on any of the switches..



Md. Mijanur Rahman Thu, 10/16/2008 - 06:13

That is cool. Then the job very simple!!

Issue the commands at my first post along with these:


interface Vlan

description **** VOICE VLAN ****

ip address x.x.x.x



interface Vlan

description **** DATA VLAN ****

ip address y.y.y.y 255.255.y.y


Then you will have:

1. seperate vlan for data and voice

2. seperate DHCP pool for data and voice

3. you have configured the access switchport for both the vlans.

You know rest of the things i believe.

Update us if it's done.

Don't need to rate anymore, it's overwhelmed already :)

Davy Ad Tue, 10/12/2010 - 23:15

Hi Mijanur,

Just want to verify , What about Default gateway ? was it defined before or need to define it again?




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