Can the DHCP server assign the IP address to the Inter-VLAN?

[mrsugabz]

Hi everyone, I'm a newbie here, looking for instructions.

As far as i know, DHCP relay is used when we wants assign the DHCP address to subnet of internetwork. But what if the hosts is in the VLAN? Is it possible for DHCP assigning their address to VLAN through network? 

Here's the topology if you need it to understand what I'm talking about..(sorry for my bad english):

 I wanna know what should I learn to solves this task. Please help me guys.

[marce1000]

  - You need to keep the concept simple : DHCP relay is defined  as a vlan property to let the hosts on that vlan find a dhcp server , 
if there is no local dhcp server on the vlan/subnet.

 M.

[Martin L]

You can attach PT file here but it must be in a zip format;

Also check CLN community PT and CCNA forums at

https://learningnetwork.cisco.com/s/communities

https://learningnetwork.cisco.com/s/topic/0TO3i0000008jYHGAY/ccna-certification-community

https://learningnetwork.cisco.com/s/topic/0TO6e000000WEorGAG/packet-tracer

Regards, ML
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[M02@rt37]

Hello @mrsugabz 

DHCP server on a different subnet/vlan than hosts ? So, DHCP relay is needed ! WHy ? because routers drop broadcast request by definition. So, the command DHCP RELAY or ip helper-address permit to "transform" the Broadcast DHCP request with a UNICAST DHCP IP packet.

[mrsugabz]

I'm sorry, but I'm not quite sure I understand what you mean (my English is a bit rusty). Could you please explain again in simpler terms for a beginner like me about what do you mean about the DHCP relay transforming a broadcast request with unicast IP?

[liviu.gheorghe]

Hello @mrsugabz ,

yes, a single DHCP server configured with multiple scopes - one for each vlan, can be used to assign IP addresses to hosts configured in different vlans.

What you will need in terms of configuration is the command ip helper-address <DHCP server IP address> configured on interface FastEthernet 0/1 of each 2911 router.

Hope this helps.

[mrsugabz]

So the DHCP pool configuration must be at least four right? For each vlan. 

When I get to the task, I'll be looking into how to configure the "DHCP relay" before. (https://www.computernetworkingnotes.com/ccna-study-guide/how-to-configure-dhcp-relay-agent-on-cisco-routers.html). 

But in that tutorial, they're not assigning the DHCP to hosts in the VLAN. Instead, it's just for the subnetwork (the switches)..
So here I'm wondering what additional commands I should use on the router so that the hosts on the VLAN can get their IP addresses from DHCP.

[liviu.gheorghe]

The tutorial you have doesn't seem to follow the network topology you have.

[Martin L]

DHCP and relay explained on Wikipedia, see section Relaying https://en.wikipedia.org/wiki/Dynamic_Host_Configuration_Protocol

The relay agent stores its own IP address, from the interface on which it has received the client's broadcast, in the GIADDR field of the DHCP packet. The DHCP server uses the GIADDR-value to determine the subnet, and subsequently the corresponding address pool, from which to allocate an IP address.

Regards, ML
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