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Occasional Contributor II

DHCP requests during Roaming

Hello,

 

I've been working on a client disconnect issue with Aruba TAC for a few weeks now. I notified them of some findings i found today while looking at our DHCP server which is Infoblox.

 

While troubleshooting with a client as this user roamed around a hospital wing I noticed his device was sending DHCPREQUEST and DHCPACK's between the DHCP server. I compared it to another user who was stationary and connected to 1 access point. I then had a 3rd user try the same thing and noticed a similar pattern. As he roamed around it seemed like his machine was constantly sending DHCPREQUEST and DHCPACKs

 

Is this a normal pattern for Wireless roaming. These users are reamaining within the same SSID,Subnet and Wireless controller. I assumed that once the Device received it's DHCP address it would keep the address as long as it was staying connected and would only ask for an IP when the client came back online and sends a DHCPDISCOVER.

Guru Elite

Re: DHCP requests during Roaming

- What kind of device is this?

- Are you using encryption?

 



Colin Joseph
Aruba Customer Engineering

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

Occasional Contributor II

Re: DHCP requests during Roaming

Colin,

 

These are all Windows 7 devices connecting using WPA2 Enterprise with Mac Authentication.

Guru Elite

Re: DHCP requests during Roaming

It seems like mac authentication is occurring every time it roams.  Did you try it without mac authentication?



Colin Joseph
Aruba Customer Engineering

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

Occasional Contributor II

Re: DHCP requests during Roaming

Colin,

 

I haven't tried it with MAC authentication. Do you think that is normal operation for Mac Authentication in regards to roaming? We are doing Mac authentication with a Cisco ACS server. I may take a look at those logs and see if i'm seeing the same amount of Mac Authentication.

 

I would think that once authenticaed on to the wireless network and put into the proper role that Mac Authentication is done at this point. Does it re-authenticate evertime it roams?

 

We have had Mac authentication with Aruba and ACS as the Authentication server for many years now. 

Guru Elite

Re: DHCP requests during Roaming

It depends.  Does the mac authentication return a VLAN, role or a Role with a VLAN?

 



Colin Joseph
Aruba Customer Engineering

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

Occasional Contributor II

Re: DHCP requests during Roaming

The Mac Auth Returns a Role. 

Guru Elite

Re: DHCP requests during Roaming

If a device does not support opportunistic key caching, it does a full authentication on each roam.


Colin Joseph
Aruba Customer Engineering

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

Occasional Contributor II

Re: DHCP requests during Roaming

Colin,

 

Thanks I spent this morning reading up a little bit on PMK and OKC. what commands can I use to view logs on a station and see if it's infact doing a full 802.1x as it roams between access points? I'm assuming Windows 7 supports OKC but the question i need to find out is if it's enabled on the client side. I checked my controller and it's enabled by default.

Guru Elite

Re: DHCP requests during Roaming

That would be "show auth-tracebuf".  http://community.arubanetworks.com/t5/Controller-Based-WLANs/What-do-the-different-numbers-mean-in-the-show-auth-tracebuf/ta-p/177860

 

The other thing is if the role that you return to the device has a VLAN assigned that could force a link up/down event for that device, so a DHCP renewal would be expected.

 

My last piece of advice is to return the the Aruba-User-Vlan attribute via radius instead of sending back a role that has a vlan assigned.

 

 



Colin Joseph
Aruba Customer Engineering

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

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