AMT/vPro MLD storms?

Phil Mayers p.mayers at
Thu Feb 6 13:21:27 CET 2014


In the last week or so, we've started to see a problem on newer PCs with 
the Intel AMT/vPro (a kind of inline out-of-band management controller, 
for those unfamiliar with it) which now "supports" IPv6... after a fashion.

The specific issues is that under certain as-yet unidentified 
conditions, two such machines which are asleep will start to emit MLD 
packets at a high rate - >1kpps. This eats a lot of CPU on the attached 
router (and can't be great for everything else, either).

The MLD packets must of course be coming from the AMT/vPro stack which 
shares the system MAC address (an unwise design decision IMO) and sort 
of shares it's IP stack. We've confirmed this by looking at the port 
speed, which is 10meg when the machine is asleep (versus 1gig when awake).

It seems that the AMT controllers "goad" each other into emitting the 
packets - if you take one offline, the other stops.

The MLD packets are of the form:

2c:44:fd:xx:xx:xx > 33:33:00:01:00:03, ethertype IPv6 (0x86dd), length 
86: fe80::2e44:fdff:fexx:xxxx > ff02::1:3: HBH ICMP6, multicast listener 
reportmax resp delay: 0 addr: ff02::1:3, length 24

...and alternate from each machine; as above, as if each machine is 
induced to emit an MLD packet by seeing the other do it.

Note the v6 LL IP is a mutated form of EUI-64 (locally-assigned bit 

Has anyone seen anything like this?


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