I used to image several Apple computer labs at my last job and we had the same 
issues.  We started using a program "Netboot Across Subnets" by Mike Bombich.  
After doing some research on his site, we were able to netboot every Mac on our 
campus regardless of which vlan they were on.  It looks like the site has 
changed a lot since I last used it but there is some good information there if 
you haven't visited it yet.  Good luck.
http://www.afp548.com/netboot/mactips/nbas.html


Joshua Humphrey
Systems Administrator I
Shared Services Center



From: Stephen Wilson [mailto:[email protected]]
Sent: Tuesday, August 09, 2011 4:58 PM
To: Enterasys Customer Mailing List
Subject: [enterasys] DHCP Snooping and Apple BSDP

Hi all,

I have an interesting problem, that at least thus far, I haven't been able to 
work around.  I have dhcp snooping enabled on my client VLAN's and under normal 
circumstances it is working properly.  This week our desktop imaging group 
tried to stand up an Apple NetBoot server to allow them to image OS X machines. 
 As far as I can tell, NetBoot uses an Apple proprietary protocol called BSDP, 
which closely resembles DHCP.  In fact, part of the Apple documentation says 
that to enable NetBoot across subnets you have to add your NetBoot server as a 
helper address on your router(s).  I have added the server as a helper address, 
and the OS X clients can now see the NetBoot server but will not boot from it.  
If I disable DHCP snooping, the entire NetBoot process works as expected.  Both 
the NetBoot and DHCP server are located through the same trusted interface on 
the switch, and the documentation states that DHCP packets received on trusted 
ports will always be forwarded.  Is there some additional undocumented security 
that DHCP snooping provides to insure packets on ports 67/68 actually are DHCP 
packets?  I have not yet done a packet capture, but my only theory is that the 
BSDP packets are being dropped because they aren't DHCP.  Has anyone else run 
into this issue and found a resolution (other than disabling DHCP snooping)?

Thanks in advance,

Stephen Wilson
Network Manager
WCU Networking and Telecommunications
828-227-3215



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