Wireless Access

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Contributor I
Posts: 25
Registered: ‎01-31-2014

Client cannot obtain dhcp address

So I am using an external DHCP server in order to lease addresses to wireless clients through the controller. Clients are only getting 169.x.x.x addresses and in the logs I see. Jul 11 14:32:55 dhcpd: DHCPDISCOVER from *MAC ADDRESS* via eth1: unknown network segment Jul 11 14:32:55 dhcpd: DHCPDISCOVER from *MAC ADDRESS* via 10.x.x.x: unknown network segment Please let me know of what other information you will need from me.

Guru Elite
Posts: 20,761
Registered: ‎03-29-2007

Re: Client cannot obtain dhcp address

What is providing DHCP?

Do you have a helper address?

 



Colin Joseph
Aruba Customer Engineering

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Contributor I
Posts: 25
Registered: ‎01-31-2014

Re: Client cannot obtain dhcp address

Windows Server is providing DHCP address, I have pinged the server from the aruba controller so there is connectivity and I have put the helper address in the IP Interface on the Controller as well.
Guru Elite
Posts: 20,761
Registered: ‎03-29-2007

Re: Client cannot obtain dhcp address

Did this ever work, or it never worked?

 



Colin Joseph
Aruba Customer Engineering

Looking for an Answer? Search the Community Knowledge Base Here: Community Knowledge Base

Contributor I
Posts: 25
Registered: ‎01-31-2014

Re: Client cannot obtain dhcp address

Well, previously we were always using the Controllers onboard DHCP Server which has an enforced limit of 512 addresses now so this is the first time I have had to use an external dhcp server....so yeah this has never worked before.
Guru Elite
Posts: 20,761
Registered: ‎03-29-2007

Re: Client cannot obtain dhcp address

Do you still have the DHCP server on the controller enabled?  If you do, disable it.  Also make sure that you have the scope defined on the DHCP server for the correct subnet.

 



Colin Joseph
Aruba Customer Engineering

Looking for an Answer? Search the Community Knowledge Base Here: Community Knowledge Base

Contributor I
Posts: 25
Registered: ‎01-31-2014

Re: Client cannot obtain dhcp address

Unfortunately the DHCP server on the controller is actually giving out addresses to a production network right now so it cannot be turned off, however I do know that the external dhcp server is set up for the correct vlan.
Guru Elite
Posts: 20,761
Registered: ‎03-29-2007

Re: Client cannot obtain dhcp address

Something else must be wrong.

 

The DHCP messages simply say that the DHCP server on the controller does not have scopes for those addresses, so it is not really helpful here.  Is the default gateway of the clients the controller?  Are you doing NAT on that subnet through the controller?

 



Colin Joseph
Aruba Customer Engineering

Looking for an Answer? Search the Community Knowledge Base Here: Community Knowledge Base

Occasional Contributor I
Posts: 8
Registered: ‎05-28-2009

Re: Client cannot obtain dhcp address

Did this ever get resolved?  We are having the same issue with one of our clients, and seeing the same error message.  One thing that I noticed in our environment is that the sourceIP of dhcp request is coming from the originating vlan interface, which is actually a vlan that is terminated by the controller and not routed in the internal network. The DHCP is being forwarded through a different vlan on the controller which is connected to the wired network.  The problem is, the server is replying with a dhcp offer, but the network doesn't have a route back to that subnet. 

 

This seems like an issue with how the DHCP helper is forwarding the DHCP request.  With the limitation that has been set on the number of DHCP IP's that the controller can issue, but the desire to still "hide" client vlan's behind the controller and not have to route the traffic internally, it is becoming necessary to send the DHCP to an external server ... but if I don't want to route these "hidden" subnets, how will the server ever get the address back to teh client if the source IP of the DHCP request is the IP of the client vlan?  That is what the "relay agent IP" is with the DHCP request.  The actual src IP of the packet should be whatever interface is used to route the traffic to the DHCP server.

 

Or am I missing something?

 

 

 

Valued Contributor II
Posts: 804
Registered: ‎12-01-2014

Re: Client cannot obtain dhcp address

HI Refuge7,

 

Can you share packet capture on the ethernet port of the DHCP server and also output of " show interface vlan <# where wireless clients are mapped> " , "show ip dhcp database" and "show ip interface brief", so that I can understand your configuration and give a solution.

 

Cheers,

Venu Puduchery

Cheers,
Venu Puduchery,
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