The stupidity of trying to "fix" DHCPv6

Ricky Beam jfbeam at
Tue Jun 14 19:50:11 CDT 2011

On Tue, 14 Jun 2011 18:16:10 -0400, Owen DeLong <owen at> wrote:
> The point of /64 is to support automatic configuration and incredibly  
> sparse host addressing.
> It is not intended to create stupidly large broadcast domains.

Several IETF (and NANOG) discussions say otherwise.  While current  
hardware doesn't handle thousands of hosts, the protocol was designed for  
a future where that's not true. (there's a future where *everything* is  
network enabled... microwave oven, doorbell, weed whacker, everything.)

> A /22 is probably about the upper limit of a sane broadcast domain, but,  
> even with a /22
> or 1022 nodes max, each sending a packet every 10 seconds you don't get  
> to 100s of PPS,
> you get 102.2pps.

As I said, DHCP isn't the only source of traffic.  Setup a 1000 node  
network today (just IPv4), and you will see a great deal of broadcast  
traffic (unless those nodes aren't doing anything.)  With IPv6, it's all  
multicast (v6 doesn't have a "broadcast address") hinged on switches  
filtering the traffic away from where it doesn't need to be.  The  
all-too-common Best Buy $20 white box ethernet switch does no multicast  
filtering at all.  Pretty much all wireless hardware sucks at multicast -  
period.  These are not things that can be fixed with a simple software  
update... if the silicon doesn't do it, *it doesn't do it*.

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