The stupidity of trying to "fix" DHCPv6

Iljitsch van Beijnum iljitsch at
Tue Jun 14 14:01:25 UTC 2011

On 14 jun 2011, at 10:20, Mikael Abrahamsson wrote:

> On the AMSIX peering LAN there is more than 100pps of ND traffic (at least there was when we checked). Since they do not do IPv6 multicast intelligent handling (MLD snooping I guess) certain highend (legacy) router platforms run into trouble because all these packets are punted to RP.

That is really pathetic. I thought that any Ethernet chip built the previous decade could filter 64 or so multicast addresses in hardware. Only when you're subscribed to more multicast groups than what your Ethernet chip can filter in hardware does the software for an IPv4-only system have to encounter IPv6 multicasts, or an IPv6 system random neighbor solicitations, which are load balanced over a wide range of multicast addresses just for this reason.

Also strange that there would be this much neighbor discovery traffic, probably the same reason AMS-IX used to have 15 kbps of ARP traffic: stale BGP peerings to addresses that no longer exist.

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