Mac OS X doesn't renew DHCP after a 802.1x re-authentication on Ethernet

Originator:mr.poche
Number:rdar://9155388 Date Originated:18/03/2011
Status:open Resolved:
Product:Mac OS X Product Version:10.6.6
Classification:Serious Bug Reproducible:
 
Summary:

After a 802.1X re-authentication, Mac OS X does DHCP Requests to the previous DHCP Server and waits 
one minute between attempts (doing a total of 3) before resorting back to a broadcasted DHCP Discove
r.

This poses problem if the VLAN assigned by the switch changed after the re-authentication. A Mac wil
l regain very slowly its network connectivity because it insists on doing the DHCP Requests where a 
DHCP Discover in the new VLAN would enable network connectivity in seconds.

Windows' behavior is it'll try 3 DHCP Requests in a row wait 2-3 seconds and if nothing came back fr
om the original server will issue broadcast a DHCP Discover.

The end result is that a Mac OS X machine will experience a loss of connectivity for 2-3 minutes whi
le for Windows its a mere Note: 0000005 seconds.

Steps to Reproduce:

- Connect a Mac OS X station on a wired switch using 802.1X for access authorization with RADIUS VLA
N assignment turned on
- Mac OS X client successfully authenticate gets VLAN A, obtains an IP
- We initiate a forced 802.1X re-authentication from the switch
- Mac OS X client successfully re-authenticate gets VLAN B
- Mac OS X client sends a DHCP Request on the server where it obtained it's last IP
- No such DHCP Server exists in this new VLAN so no one will reply
- After a couple of minutes the Mac OS X client abandon the DHCP Requests and will do a DHCP Discove
r

Expected Results:

If the DHCP Requests have no reply within a couple of seconds, the OS should do a DHCP Discover righ
t away to obtain an IP.

Actual Results:

It does 3 DHCP Requests and wait for one minute each for a reply leading to a 3 minutes of no networ
k connectivity even though it could work.

Regression:

10.5 and previous 10.6 are also affected but we made sure it was reproducible with 10.6.6

Notes:

A related problem existed for Wireless 802.1X and Wireless MAC Authentication in general but it has 
been fixed in 10.6.5.

Comments


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