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Occasional Contributor I
Posts: 6
Registered: ‎09-15-2014

Configuring external DHCP server in different VLANs

My situation is a little bit complicated but I will try my best to describe it. I'm trying to configure an external DHCP server for our Aruba 3400 controller. Currently the controller is connected to our core switch (which is a Cisco switch), and the controller along with other servers are in VLAN 149. Clients connected to the APs are in VLAN 150 and are getting IP from DHCP server in controller. However, we are asked to manage all DHCP leases (wired and wireless access) in one DHCP server. The new DHCP server is in a virtual machine and have two network interface, one's address is in VLAN 149 and another is in VLAN 118 (we are planning to put all public network access in it). The host is connected to core switch and is in VLAN 149

Now when I plug PC into the core switch, it can acquire IP address from the VM. However when I connect from wireless I can't. I think that I missed some configurations in VLAN. Do I need to set the port mode in controller to trunk? Or how should I configure the controller and the core switch properly to let the DHCP broadcast go through them? Our network plans are in the attachment (sorry for my bad drawing skills).

 

Thanks in advance.

Aruba
Posts: 1,296
Registered: ‎08-29-2007

Re: Configuring external DHCP server in different VLANs

you just need to put in an ip-helper address to point to the DHCP server.  Put this in your vlan 150.

 

interface vlan 150
ip helper-address <dhcp-server ip>

If my post is helpful please give kudos, or mark as solved if it answers your post.

ACCP, ACMP, ACMX #294
mclarke@arubanetworks.com
Occasional Contributor I
Posts: 6
Registered: ‎09-15-2014

Re: Configuring external DHCP server in different VLANs

Do I have to set anything (Port Mode, VLAN ID) at the Ports tab in the controller?

 

Thanks for the fast reply!

Contributor I
Posts: 36
Registered: ‎05-12-2011

Re: Configuring external DHCP server in different VLANs

[ Edited ]

davidfangf wrote:

Do I have to set anything (Port Mode, VLAN ID) at the Ports tab in the controller?

 

Thanks for the fast reply!


Have you configured the VLAN in the ArubaOS Configuration -> Network -> VLANS -> VLAN ID tab? You don't need to give it an IP address at the moment depending on what you are doing with it, you just need to define the VLAN.

 

Also, am I reading the diagram correctly that port on the Aruba is in access mode on VLAN 149? In order for the Aruba controller to pass network traffic tagged with VLAN 150, you will need to switch the Aruba and Core switch port for the Aruba to a trunk. This will obviously cause some downtime.

 

Edit: I'll edit and say that there seem to be some missing pieces to this puzzle. Verify you have the ability to ping the accross VLANS from the aruba controller, and the core switch has the ability to ping all the IP addresses of the aruba controller.

Occasional Contributor I
Posts: 6
Registered: ‎09-15-2014

Re: Configuring external DHCP server in different VLANs

Yes, currently the port on Aruba is in access mode on VLAN 149. I didn't set trunk mode on core switch, and I couldn't ping between VLANs (from Aruba to DHCP server). I will check it tomorrow. Thanks!

Occasional Contributor I
Posts: 6
Registered: ‎09-15-2014

Re: Configuring external DHCP server in different VLANs

I set the port on core switch, Aruba and D-Link layer 2 switch to trunk and native VLAN is 149. However I still can't ping from Aruba to my DHCP server. Is there anything wrong in my config?

Aruba
Posts: 1,296
Registered: ‎08-29-2007

Re: Configuring external DHCP server in different VLANs

From what you say, the Aruba, switch and DHCP are all on vlan 149.

 

You should be able to ping the dhcp in that case.  Is it a windows dhcp?  Check there is nothing silly like Windows firewall blocking it. 

 

Can you run wireshark on the dhcp?  What are you seeing in there if you try to ping it from the Aruba?


If my post is helpful please give kudos, or mark as solved if it answers your post.

ACCP, ACMP, ACMX #294
mclarke@arubanetworks.com
Occasional Contributor I
Posts: 6
Registered: ‎09-15-2014

Re: Configuring external DHCP server in different VLANs

DHCP is running in Arch Linux. I can ping the VLAN 149 IP from Aruba but not the VLAN 118 IP. I think that the VLAN settings in VM host's virtual switch are incorrect.
Aruba
Posts: 1,296
Registered: ‎08-29-2007

Re: Configuring external DHCP server in different VLANs


davidfangf wrote:
DHCP is running in Arch Linux. I can ping the VLAN 149 IP from Aruba but not the VLAN 118 IP. I think that the VLAN settings in VM host's virtual switch are incorrect.

Either that or a routing issue.


If my post is helpful please give kudos, or mark as solved if it answers your post.

ACCP, ACMP, ACMX #294
mclarke@arubanetworks.com
Occasional Contributor I
Posts: 6
Registered: ‎09-15-2014

Re: Configuring external DHCP server in different VLANs

Finally solved this problem. I wasn't aware of VLAN config on VM host's virtual switch. Thanks for your help!

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