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Today's Topics:
1. MAC randomisation and DHCP pools (Mike Richardson)
2. Re: MAC randomisation and DHCP pools (glenn.satch...@uniq.com.au)
3. Re: MAC randomisation and DHCP pools (Mike Richardson)
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Message: 1
Date: Fri, 24 Jul 2020 10:10:54 +0100
From: Mike Richardson <mike.richard...@manchester.ac.uk>
To: dhcp-users@lists.isc.org
Subject: MAC randomisation and DHCP pools
Message-ID: <20200724091054.ga8...@jadzia.mcc.ac.uk>
Content-Type: text/plain; charset=us-ascii
Hiya,
Given Apple's decision to enable randomisation of MACs on IOS devices every
24 hours, I was wondering what effect this would have on DHCP?
For example, if you have a pool of 100 IPs, 50 IOS devices and leases set to
7 days.
At the moment the same 50 IPs would be assigned each day. Post-randomisation
50 would be assigned on day 1. On day 2, my understanding is that the devices
would REQUEST their previous IPs and be NACKed, then do a DISCOVER and get a
new lot of 50 addresses. What I'm unsure about is what happens on day 3? 'no
free leases', a ping check and reallocation of old addresses or something
else?
Can anyone enlighten me?
Thanks,
Mike
--
Mike Richardson
------------------------------
Message: 2
Date: Fri, 24 Jul 2020 19:48:54 +1000
From: glenn.satch...@uniq.com.au
To: Users of ISC DHCP <dhcp-users@lists.isc.org>
Subject: Re: MAC randomisation and DHCP pools
Message-ID: <d601ed1942208d56825051e2602c3...@uniq.com.au>
Content-Type: text/plain; charset=US-ASCII; format=flowed
Hi Mike,
This is not something new, it has been around since IOS 8 in 2014. I
think this page summarises how it works and has links to Apple's site
with more details.
https://9to5mac.com/2014/09/26/more-details-on-how-ios-8s-mac-address-randomization-feature-works-and-when-it-doesnt/
It appears that it randomises the MAC address when the device is
passively scanning for networks and other particular settings are
enabled or disabled, so systems can't use the MAC address to
persistently track wherever you go. However, it seems that any
associations/joining of networks is based on the actual MAC address.
Or am I talking about something else entirely different?
regards,
Glenn
On 2020-07-24 19:10, Mike Richardson wrote:
> Hiya,
>
> Given Apple's decision to enable randomisation of MACs on IOS devices
> every
> 24 hours, I was wondering what effect this would have on DHCP?
>
> For example, if you have a pool of 100 IPs, 50 IOS devices and leases
> set to
> 7 days.
>
> At the moment the same 50 IPs would be assigned each day.
> Post-randomisation
> 50 would be assigned on day 1. On day 2, my understanding is that the
> devices
> would REQUEST their previous IPs and be NACKed, then do a DISCOVER and
> get a
> new lot of 50 addresses. What I'm unsure about is what happens on day
> 3? 'no
> free leases', a ping check and reallocation of old addresses or
> something
> else?
>
> Can anyone enlighten me?
>
> Thanks,
>
> Mike
------------------------------
Message: 3
Date: Fri, 24 Jul 2020 11:59:09 +0100
From: Mike Richardson <mike.richard...@manchester.ac.uk>
To: Users of ISC DHCP <dhcp-users@lists.isc.org>
Subject: Re: MAC randomisation and DHCP pools
Message-ID: <20200724105909.gb8...@jadzia.mcc.ac.uk>
Content-Type: text/plain; charset=us-ascii
> Hi Mike,
>
> This is not something new, it has been around since IOS 8 in 2014. I think
> this page summarises how it works and has links to Apple's site with more
> details.
>
> https://9to5mac.com/2014/09/26/more-details-on-how-ios-8s-mac-address-randomization-feature-works-and-when-it-doesnt/
>
> It appears that it randomises the MAC address when the device is passively
> scanning for networks and other particular settings are enabled or disabled,
> so systems can't use the MAC address to persistently track wherever you go.
> However, it seems that any associations/joining of networks is based on the
> actual MAC address.
>
> Or am I talking about something else entirely different?
Something new I believe:
https://wifinowglobal.com/news-and-blog/new-private-wi-fi-address-iphone-feature-could-severely-impact-the-wi-fi-industry-expert-says/?mc_cid=9ff8988c11&mc_eid=000d85d9e3
https://support.apple.com/en-us/HT211227
Apple, in IOS14, are going to implement the changing of MACs every 24 hours
as the default, and different ones for each SSID, I believe.
I'm just trying to evaluate the impact on things like DHCP, but I'm not sure
about exactly what happens when pools are, sort of, exhausted.
Thanks,
Mike
--
Mike Richardson
** This email address will no longer work after 30th September 2018 **
** Please use doc...@perpetual.name instead for personal email **
** For work related communication use mike.richard...@jisc.ac.uk **
------------------------------
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