Hi All,

Looks like we have more informations about this.

I tested (and confirmed) this behavior using OSX 10.6.3.  However, I 
updated to 10.6.5 this afternoon, and the behavior is now gone.

On dissociation, we now see the following :
- We deauth the Mac OS X client
- Mac OS X client reconnects, get a different VLAN assigned
- it waits for its DHCP lease to expire
- The client did some DHCP Request to the broadcast IP (255.255.255.255) 
(3 times) with a 2 sec interval
- The client issued a DHCP Discover
- DHCP Server responds
- Mac OS X client has an IP in the right VLAN

I hope it will help some of you.

On 10-12-01 1:24 PM, Olivier Bilodeau wrote:
> Hi,
>
> We have seen on and off reports that Mac OS X registration is painful
> with PacketFence and that in most cases a reboot, disconnecting and
> reconnecting the SSID or waiting for several minutes was the 'fix'.
>
> At some point we had problems with 10.5 and we were told that they were
> supposedly fixed in 10.6..
>
> Lately the problem reoccurred and we decided to properly document it and
> take the time to see exactly what's going on. If it's hour fault, Mac OS
> X's fault and if something could be done about it.
>
> I filed a ticket earlier with the details. Here it is:
>
> http://www.packetfence.org/bugs/view.php?id=1132
> #1132: Mac OS X DHCP issues after a VLAN change on wireless networks
>
> Based on the setup we are sometimes able to reproduce the problem 100%
> of the time or not at all.
>
> The issue: Mac OS X after a wireless deauthentication (desassociation)
> doesn't do a DHCP Discover.
>
> What happens:
> - we deauth the Mac OS X client
> - Mac OS X client reconnects, get a different VLAN assigned
> - it waits for its DHCP lease to expire
> - it then does DHCP Request on the server where it obtained it's last IP
> - a default DHCP server configuration will not reply to that DHCP
> Request thinking it's not for him (wrong IP information on wrong interface)
> - after a couple of minutes the Mac OS X client abandon the DHCP
> Requests and do a DHCP Discover
> - DHCP Server responds
> - Mac OS X client has an IP in the right VLAN
>
> Because of the lease expiry delays and the DHCP Request timeout delays,
> it takes several minutes to gain network access. This is unacceptable.
> On Windows, everything works fine.
>
> Expected:
> - we deauth the Mac OS X client
> - Mac OS X client reconnects, get a different VLAN assigned
> - Mac OS X issues a DHCP Discover (it's in a new network after all!)
> - it gets an IP in the good VLAN
>
> Workaround:
> We are working on a workaround which involves sending a DHCP NAK
> (non-acknowledge) if we see a DHCP Request coming with the wrong IPs on
> the wrong interface. This way we reduce the delay window only to the
> dhcp lease timeout. Here's the flow with the workaround:
> - we deauth the Mac OS X client
> - Mac OS X client reconnects, get a different VLAN assigned
> - it waits for its DHCP lease to expire
> - it then does DHCP Request on the server where it obtained it's last IP
> - DHCP Server sends a DHCP NAK to the client
> - Mac OS X client does a DHCP Discover
> - DHCP Server responds
> - Mac OS X client has an IP in the right VLAN
>
> As stated earlier, some setups are affected some aren't so we aren't
> sure where the interaction change. Here's a list of variables to look after:
> - ip-helpers based or not (vs bridged layer2 to dhcp)
> - DHCP Server based on Windows or Linux
> - Using a Controller or fat Access Points
>
> We are investigating on this but any findings would help us a lot!
>
> Thanks,


-- 
Francois Gaudreault
[email protected]  ::  +1.514.447.4918 (x130) ::  www.inverse.ca
Inverse inc. :: Leaders behind SOGo (www.sogo.nu) and PacketFence 
(www.packetfence.org)


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