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

Emulation
Level 1
Level 1

Good morning everyone, I'm new here, and I'm looking for help. 
As you can see from the attached file, I'm trying to share the DHCP services (server is in vlan 10 - server) to the other two (100 -vlan1 e 200 -vlan2).

I configured 3 pools, one for each vlan, and so I configured the router. 
Using the command 

interface vlan NUMBER

I can then use the commands

ip helper-address 192.168.1.6 (DHCP server's address)
ip Ip.Ip.Ip.Ip Sub.Sub.Sub.Sub (e.g. assigned to the port used for vlan1)

then I try to configure the ip usign the DHCP service, with no results (APIPA is started instead).

Am I forgetting something?
Thanks in advance for your help.

1 Accepted Solution

Accepted Solutions

luis_cordova
VIP Alumni
VIP Alumni

Hi @Emulation ,

 

I have reviewed your exercise and I have found some things that prevented you from achieving what you were looking for.
On the switch:
-The access interfaces of the final devices must be associated with the corresponding vlan.
-The interface that connects the switch with the router must be in trunk mode.

On the router:
-The HWIC that you used (HWIC-4ESW) is an L2 switch module, so it is not useful to divide the networks using VLANs.
For this, you must use layer 3 interfaces.
For this, you can use an Ethernet HWIC (WIC-1ENET) to add a third L3 interface.

-Once you add that HWIC, you must configure subinterfaces in each L3 interface, this is to be able to assign the corresponding vlan number to the network.
-In those subinterfaces, you must add the ip helper-address command, pointing to the IP address of the DHCP server.

 

With these changes, your exercise will work without problems.
I have attached the exercise to you, working with the changes mentioned above.

 

Remember to mark the correct answers as solved, because that helps other users with similar doubts.

 

Regards

View solution in original post

6 Replies 6

Jaderson Pessoa
VIP Alumni
VIP Alumni
Hello, your configuration is empty.

I will recreate an exemple for you.
Jaderson Pessoa
*** Rate All Helpful Responses ***

Jaderson Pessoa
VIP Alumni
VIP Alumni

Hello @Emulation ,

 

check attached file with simple exemple of ip helper address.

 

 

Good lucky

Jaderson Pessoa
*** Rate All Helpful Responses ***

Hello
I am assuming the clients are attached to access switches towards the rtr/l3 switch where the server service resides and all the vlan trunks etc... are in place if so then you wont require any helper address for the dhcp server isnt remote and is avaible for all clients on their specific vlans

Example dhcp

ip dhcp pool 1
network 10.1.1.0 255.255.255.0
default-router 10.1.1.1
dns-server 1.1.1.1 2.2.2.2 3.3.3.3
domain-name exmaple.com
lease 0 8

ip dhcp pool 2-3
network 10.2.2.0 255.255.255.0
network 10.3.2.0 255.255.254.0 secondary
override default-router 10.3.3.1
default-router 10.2.2.1
dns-server 1.1.1.1 2.2.2.2 3.3.3.3
domain-name example.com
lease 0 8

ip dhcp excluded-address 10.1.1.1
ip dhcp excluded-address 10.2.2.1
ip dhcp excluded-address 10.3.3.1


Please rate and mark as an accepted solution if you have found any of the information provided useful.
This then could assist others on these forums to find a valuable answer and broadens the community’s global network.

Kind Regards
Paul

luis_cordova
VIP Alumni
VIP Alumni

Hi @Emulation ,

 

I have reviewed your exercise and I have found some things that prevented you from achieving what you were looking for.
On the switch:
-The access interfaces of the final devices must be associated with the corresponding vlan.
-The interface that connects the switch with the router must be in trunk mode.

On the router:
-The HWIC that you used (HWIC-4ESW) is an L2 switch module, so it is not useful to divide the networks using VLANs.
For this, you must use layer 3 interfaces.
For this, you can use an Ethernet HWIC (WIC-1ENET) to add a third L3 interface.

-Once you add that HWIC, you must configure subinterfaces in each L3 interface, this is to be able to assign the corresponding vlan number to the network.
-In those subinterfaces, you must add the ip helper-address command, pointing to the IP address of the DHCP server.

 

With these changes, your exercise will work without problems.
I have attached the exercise to you, working with the changes mentioned above.

 

Remember to mark the correct answers as solved, because that helps other users with similar doubts.

 

Regards

So, if I understand the problem rightly, all my problems are caused by the fact I'm not using encapsulation on the same interface (e.g. fastEthernet 0/1.10)?

Hi @Emulation ,

 

Not only that, since as indicated, there were several themes to change.

These indicate them in the previous message.

About the encapsulation in subinterfaces, both devices, the switches and the routers use vlan 1 for default, but, when using other vlan, you must specify to the router what vlan must be tag in each subinterface.

 

Regards 

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