Enabling DHCP Server on a router

[haji_akhundov]

Hi everyone!

I have 4 subinterfaces on FastEthernet 0/0, listed below.

How can I make such that each of them has a DHCP server enabled?

!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

interface FastEthernet0/0.4

description VLAN20-Management

encapsulation dot1Q 20

ip address 10.0.0.1 255.255.255.0           < -- DHCP for this one

!

interface FastEthernet0/0.5

description VLAN40-VoIP

encapsulation dot1Q 40

ip address 10.0.1.1 255.255.255.0           < -- DHCP for this one

!

interface FastEthernet0/0.6

description VLAN60-VIP_Users

encapsulation dot1Q 60

ip address 10.0.2.1 255.255.255.0            < -- DHCP for this one

!

interface FastEthernet0/0.7

description VLAN80-Hosts

encapsulation dot1Q 80

ip address 10.0.3.1 255.255.255.0            < -- DHCP for this one

!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

Thanks! Hope to get some good advice!

[cadet alain]

Hi,

the dhcp service is listening on every interface but you need to configure a pool for each subnet you want to lease out addresses.

Regards.

Alain

Don't forget to rate helpful posts.

[haji_akhundov]

Dear alain,

Thanks for the reply.

I tried what Ahmed suggested and what you actually suggested also. I still have a theoretical question in mind:

How does the router know which pool to use on which interface?

Regards

[p.mcgowan]

you can create a separate dhcp pool for each of the subnets you require.

the following doc shows a good example

http://www.cisco.com/en/US/docs/ios/12_0t/12_0t1/feature/guide/Easyip2.html#wp25541

please rate helpful posts

[haji_akhundov]

That's a nice document there. Thanks for sharing. =)

[AhmedSonba · Accepted solution]

Hello Haji,

You can do it for example like the following :

ip dhcp excluded-address 10.0.3.1

ip dhcp excluded-address 10.0.2.1

ip dhcp excluded-address 10.0.1.1

ip dhcp excluded-address 10.0.0.1

ip dhcp pool Management

network  10.0.0.1 /24

domain-name Management .com

default-router  10.0.0.1

ip dhcp pool VOIP

Network 10.0.1.1 /24         

domain-name VOIP.com

default-router  10.0.1.1

ip dhcp pool VIP

network 10.0.2.1/24

domain-name Vip.com

default-router  10.0.2.1

ip dhcp pool Hosts

network  10.0.3.1/24

domain-name hosts.com

default-router  10.0.3.1

Hope it will help

Ahmed Sonba

[haji_akhundov]

Thank you Ahmed.

This did help actually. I tried it on packet tracer and it works fine. But I'm still wondering how does the router know which pool to use on which interface, have any clue?

Regards

[XIE YAO]

Hi Haji,

As mentioned by Alain, the router will listening the DHCP request from each of these interface, let say if one request if heard from FastEthernet0/0.5, router will accordingly allocate ip address based the interface ip, in this case, 10.0.1.0/24.

Hope this helps.

[haji_akhundov]

okay. it makes sense. thanks. =)