Sharing the same DHCP server on multiple VLAN's on Packet Tracer

[faisal alkhajah]

Good Morning. I have a project in which I want to build a small university network but I am having issues with the configuration of the DHCP server as a cannot get automatically assign it to all PC.

I Have configured 4 pools for each switch and department.

I really could use the help I will attach my packet tracer below. Thank you for the help.

[MHM Cisco World]

use 
DHCP relay

config IP helper point to your DHCP Server 

[faisal alkhajah]

Hi, 

do i use the ip helper in the router or the main switch or i have to do for all of the switches and routers?

this is where i am having the issues.

[Flavio Miranda · Accepted solution]

There was some mistakes on the project. I fixed  the most importants and you can see that PC7 is working.  You can use it as example to fix everything else.

Things wrong:

- Uplink between switch where the DHCP server is connectec and the router was in access. Need to be trunk.

-You dont need vlan on the router "Main Router"

-You did right the subinterface on the Main Router but then you create DHCP in a different range.  The DHCP scope needs to be on the same network of the router subinterface. Look at the DHCP server I created a new scope and called My_scope. See that it is on the same range as subinterface 192.168.20.0/24

- The DHCP helper address must point to the DHCP server IP address, You pointed to 192.168.0.1 which is the Rotuer IP address.

I think it´s all. 

Use my file to compare with yours and good studies.

[faisal alkhajah]

Thank you for the help, i have seen the document that you attached and i am sorry i still cant figure out the rest. Trying to do as you said but the same problems occur in which the DHCP fails. Could you please maybe send screenshots of the configuration or elaborate more. Thank you again.

[Flavio Miranda]

Hi

 Find attached the show run of the devices involved and the print of the DHCP server.  

Any doubt just ask.

[faisal alkhajah]

Sorry to bother you again but it would still not work, if you can be kind and do the same as you did for pc7 to one of the pc for each department as I could not get it to work, cant seem to figure it out. Thank you for your help and I highly appreciate it.

[faisal alkhajah]

nevermind i have found what was the problem thanks to your screenshots thank you very much

[Flavio Miranda]

Alright. On this PKT file, we have on PC working in each vlan. 

Try it now and let me know.

[MHM Cisco World]

@Flavio Miranda @faisal alkhajah 
Mr.Favio 
config is perfect except that the IP helper must point to DHCP IP server.
I correct config hope this is solve issue.

interface FastEthernet0/1.1

 encapsulation dot1Q 10

 ip address 192.168.10.1 255.255.255.0

 ip helper-address 192.168.20.1

!

interface FastEthernet0/1.2

 encapsulation dot1Q 20

 ip address 192.168.20.1 255.255.255.0

 ip helper-address 192.168.20.1

!

interface FastEthernet0/1.3

 encapsulation dot1Q 30

 ip address 192.168.30.1 255.255.255.0

 ip helper-address 192.168.20.1

!

interface FastEthernet0/1.4

 encapsulation dot1Q 40

 ip address 192.168.40.1 255.255.255.0

 ip helper-address 192.168.20.1

[Georg Pauwen]

Hello,

since I was working on the file, I might as well send what I have come up with. There were numerous mistakes:

--> wrong IP helper address on the subinterfaces (needs to be 192.168.0.2)

--> wrong trunk configurations

--> wrong IP address pools on the DHCP server (default gateways in the pools needs to match the IP addresses of the subinterfaces)

--> wrong/missing switchport Vlan assignments

--> missing management Vlan in the entire network

--> duplicate Vlan 10/20 interfaces on the router

Attached the revised file (saved in PT version 8.1.1, make sure you are using the same version)...