100% CPU usage after turning on IPv6?
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Upgraded this morning and the system ran fine, so after about 2 hours I turned on IPv6 and after finally getting it working, I noticed that the CPU was running 100%. So I thought maybe I bunged something up and restarted. CPU dropped to 50% and continued that way. Looked at top and did not notice anything conclusive (idle, PHP and dhcp were the top of top -SH). So on a lark I went into the wan interface and changed the IPV6 configuration type from DHCP6 to None, and after about a minutes the CPU usage dropped off to the normal < 2%. See the attached graph. The upgrade was at 8:00, finished the DHCPv6 changes around 10:30, and turned off wan DHCPv6 when CPU when to essentially zero. Then I turned the wan IPV6 config back to DHCP6, reset the DHCP client config (which was reset) to delegation size 60 and send prefix hint. It seems to be running fine for about 5 minutes, then CPU Usage went to 100% and I get a log of repeatable DHCP requests (attached).
Traffic logs did not show anything unusual.
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You have some Apple junk on your network?
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Turns out it was an HP LaserJet printer. Rebooting the printer solved the problem. Have talked with support, because I still think it is a problem that the firewall did not limit its responses and allowed the device to essentially do a DOS attack. You can see the firewall responses in the log posted.
The key was using the NDT table under diagnostics to tie the IPv6 address to a MAC address.
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You have some Apple junk on your network?
Yes I have a bunch of crap Apple, crap HP, crap Linux, crap freeBSD, crap nintendo, crap Denon, crap Nest, crap silicondust, crap iTach, and crap Zoom stuff on the network.
Your point?
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My point is that several people recently reported Bitten Fruit products to behave like nuts regarding DHCP. Notably when both wired and wireless was enabled on them.
Traffic logs did not show anything unusual.
ORLY? You consider renewing IP lease multiple times per second normal? :o Find the offending device in the NDP table and unplug it. After than, you will probably need to delete the dhcpv6 leases file manually to get back to sane state.