The stupidity of trying to "fix" DHCPv6

sthaug at sthaug at
Thu Jun 16 18:37:12 UTC 2011

> "Ethernet doesn't scale because of large amounts of broadcast traffic."
> We started to introduce multicast, and multicast-aware switches in
> IPv4; in IPv6 there is no broadcast traffic.  We won't be able to
> scale networks up until we can turn off IPv4,

In other words, probably not for another decade at least?

> but once we can IPv6
> will be able to grow much larger in terms of per-LAN.   The best
> practice of no more than 512 per broadcast domain will seem very
> outdated at that point; especially when you add in multicast flood
> protection, the available bandwidth goes up, and performance of
> network interfaces improves.

Yes and no. If you remove the broadcast traffic you can *in theory*
scale higher. However, this does nothing for the difficulty of L2
troubleshooting, which is a real problem in large flat L2 networks.

> The link you pointed to is talking about flat networks of tens of
> thousands of hosts; that might be excessive right now...  But I can
> certainly see an IPv6-only LAN (with some filtering to make sure ARP
> and IPv4 traffic is dropped at the port) scaling easily to thousands
> of hosts with today's hardware.

I'm afraid I remain sceptical, unless we come up with significantly
improved methods for L2 troubleshooting.

Steinar Haug, Nethelp consulting, sthaug at

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